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	$100.53	3.584%	$104.133	$104.13	$104.15	$104.10
Purchase #2	$75.89	9.107%	$82.8013	$82.80	$82.80	$82.80
Purchase #3	$177.54	10.297%	$195.8213	$195.82	$195.80	$195.80
Purchase #4	$165.83	7.397%	$178.0964	$178.10	$178.10	$178.10
Purchase #5	$123.74	6.424%	$131.6891	$131.69	$131.70	$131.70
Purchase #6	$96.54	7.759%	$104.0305	$104.03	$104.05	$104.00
Purchase #7	$197.32	8.191%	$213.4825	$213.48	$213.50	$213.50
7 purchase totals =	$937.39		$1,010.0541	$1,010.05	$1,010.10	$1,010.00