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	$186.53	5.390%	$196.584	$196.58	$196.60	$196.60
Purchase #2	$168.52	12.640%	$189.8209	$189.82	$189.80	$189.80
Purchase #3	$110.53	6.348%	$117.5464	$117.55	$117.55	$117.50
Purchase #4	$222.97	9.841%	$244.9125	$244.91	$244.90	$244.90
Purchase #5	$50.40	7.690%	$54.2758	$54.28	$54.30	$54.30
Purchase #6	$89.80	5.464%	$94.7067	$94.71	$94.70	$94.70
Purchase #7	$150.79	9.219%	$164.6913	$164.69	$164.70	$164.70
7 purchase totals =	$979.54		$1,062.5376	$1,062.54	$1,062.55	$1,062.50