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	$233.41	13.458%	$264.8223	$264.82	$264.80	$264.80
Purchase #2	$90.48	10.248%	$99.7524	$99.75	$99.75	$99.80
Purchase #3	$6.64	7.646%	$7.1477	$7.15	$7.15	$7.10
Purchase #4	$160.84	10.720%	$178.082	$178.08	$178.10	$178.10
Purchase #5	$180.72	12.865%	$203.9696	$203.97	$203.95	$204.00
Purchase #6	$38.39	4.445%	$40.0964	$40.10	$40.10	$40.10
Purchase #7	$117.91	11.400%	$131.3517	$131.35	$131.35	$131.40
7 purchase totals =	$828.39		$925.2221	$925.22	$925.20	$925.30