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	$232.47	13.294%	$263.3746	$263.37	$263.35	$263.40
Purchase #2	$59.41	9.815%	$65.2411	$65.24	$65.25	$65.20
Purchase #3	$52.39	3.276%	$54.1063	$54.11	$54.10	$54.10
Purchase #4	$198.33	11.178%	$220.4993	$220.50	$220.50	$220.50
Purchase #5	$83.46	10.604%	$92.3101	$92.31	$92.30	$92.30
Purchase #6	$223.47	9.241%	$244.1209	$244.12	$244.10	$244.10
Purchase #7	$142.55	11.292%	$158.6467	$158.65	$158.65	$158.60
7 purchase totals =	$992.08		$1,098.2990	$1,098.30	$1,098.25	$1,098.20