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	$176.85	6.256%	$187.9137	$187.91	$187.90	$187.90
Purchase #2	$122.89	4.410%	$128.3094	$128.31	$128.30	$128.30
Purchase #3	$53.87	7.236%	$57.768	$57.77	$57.75	$57.80
Purchase #4	$177.56	10.700%	$196.5589	$196.56	$196.55	$196.60
Purchase #5	$120.25	10.743%	$133.1685	$133.17	$133.15	$133.20
Purchase #6	$8.43	3.219%	$8.7014	$8.70	$8.70	$8.70
Purchase #7	$174.54	4.178%	$181.8323	$181.83	$181.85	$181.80
7 purchase totals =	$834.39		$894.2522	$894.25	$894.20	$894.30