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	$52.64	8.381%	$57.0518	$57.05	$57.05	$57.10
Purchase #2	$90.86	5.715%	$96.0526	$96.05	$96.05	$96.10
Purchase #3	$99.54	6.199%	$105.7105	$105.71	$105.70	$105.70
Purchase #4	$45.44	12.624%	$51.1763	$51.18	$51.20	$51.20
Purchase #5	$147.51	5.234%	$155.2307	$155.23	$155.25	$155.20
Purchase #6	$139.67	11.131%	$155.2167	$155.22	$155.20	$155.20
Purchase #7	$237.30	7.409%	$254.8816	$254.88	$254.90	$254.90
7 purchase totals =	$812.96		$875.3202	$875.32	$875.35	$875.40