Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$212.62	5.150%	$223.5699	$223.57	$223.55	$223.60
Purchase #2	$122.30	10.644%	$135.3176	$135.32	$135.30	$135.30
Purchase #3	$176.73	6.550%	$188.3058	$188.31	$188.30	$188.30
Purchase #4	$139.34	3.723%	$144.5276	$144.53	$144.55	$144.50
Purchase #5	$124.40	5.631%	$131.405	$131.41	$131.40	$131.40
Purchase #6	$144.47	4.851%	$151.4782	$151.48	$151.50	$151.50
Purchase #7	$152.51	11.267%	$169.6933	$169.69	$169.70	$169.70
7 purchase totals =	$1,072.37		$1,144.2974	$1,144.31	$1,144.30	$1,144.30