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	$97.69	3.543%	$101.1512	$101.15	$101.15	$101.20
Purchase #2	$239.95	6.173%	$254.7621	$254.76	$254.75	$254.80
Purchase #3	$189.71	3.781%	$196.8829	$196.88	$196.90	$196.90
Purchase #4	$91.37	4.762%	$95.721	$95.72	$95.70	$95.70
Purchase #5	$80.79	3.211%	$83.3842	$83.38	$83.40	$83.40
Purchase #6	$153.71	11.810%	$171.8632	$171.86	$171.85	$171.90
Purchase #7	$209.88	3.703%	$217.6519	$217.65	$217.65	$217.70
7 purchase totals =	$1,063.10		$1,121.4165	$1,121.40	$1,121.40	$1,121.60