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	$152.50	12.343%	$171.3231	$171.32	$171.30	$171.30
Purchase #2	$156.80	10.693%	$173.5666	$173.57	$173.55	$173.60
Purchase #3	$185.87	10.344%	$205.0964	$205.10	$205.10	$205.10
Purchase #4	$48.57	13.871%	$55.3071	$55.31	$55.30	$55.30
Purchase #5	$245.97	7.125%	$263.4954	$263.50	$263.50	$263.50
Purchase #6	$74.94	6.448%	$79.7721	$79.77	$79.75	$79.80
Purchase #7	$90.56	9.571%	$99.2275	$99.23	$99.25	$99.20
7 purchase totals =	$955.21		$1,047.7882	$1,047.80	$1,047.75	$1,047.80