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	$179.55	13.539%	$203.8593	$203.86	$203.85	$203.90
Purchase #2	$79.88	13.234%	$90.4513	$90.45	$90.45	$90.50
Purchase #3	$211.98	4.842%	$222.2441	$222.24	$222.25	$222.20
Purchase #4	$205.30	12.341%	$230.6361	$230.64	$230.65	$230.60
Purchase #5	$77.31	6.734%	$82.5161	$82.52	$82.50	$82.50
Purchase #6	$135.47	4.482%	$141.5418	$141.54	$141.55	$141.50
Purchase #7	$203.37	4.390%	$212.2979	$212.30	$212.30	$212.30
7 purchase totals =	$1,092.86		$1,183.5466	$1,183.55	$1,183.55	$1,183.50