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	$155.95	12.804%	$175.9178	$175.92	$175.90	$175.90
Purchase #2	$113.33	4.722%	$118.6814	$118.68	$118.70	$118.70
Purchase #3	$118.44	10.765%	$131.1901	$131.19	$131.20	$131.20
Purchase #4	$196.77	4.144%	$204.9241	$204.92	$204.90	$204.90
Purchase #5	$90.65	10.437%	$100.1111	$100.11	$100.10	$100.10
Purchase #6	$73.80	12.354%	$82.9173	$82.92	$82.90	$82.90
Purchase #7	$11.49	10.515%	$12.6982	$12.70	$12.70	$12.70
7 purchase totals =	$760.43		$826.4400	$826.44	$826.40	$826.40