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	$31.94	4.145%	$33.2639	$33.26	$33.25	$33.30
Purchase #2	$47.25	10.497%	$52.2098	$52.21	$52.20	$52.20
Purchase #3	$100.88	3.371%	$104.2807	$104.28	$104.30	$104.30
Purchase #4	$56.73	6.467%	$60.3987	$60.40	$60.40	$60.40
Purchase #5	$176.99	12.250%	$198.6713	$198.67	$198.65	$198.70
Purchase #6	$153.92	11.345%	$171.3822	$171.38	$171.40	$171.40
Purchase #7	$79.58	12.238%	$89.319	$89.32	$89.30	$89.30
7 purchase totals =	$647.29		$709.5256	$709.52	$709.50	$709.60