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	$41.90	3.658%	$43.4327	$43.43	$43.45	$43.40
Purchase #2	$55.33	4.745%	$57.9554	$57.96	$57.95	$58.00
Purchase #3	$212.89	9.679%	$233.4956	$233.50	$233.50	$233.50
Purchase #4	$85.67	4.371%	$89.4146	$89.41	$89.40	$89.40
Purchase #5	$8.61	8.512%	$9.3429	$9.34	$9.35	$9.30
Purchase #6	$243.31	11.464%	$271.2031	$271.20	$271.20	$271.20
Purchase #7	$181.89	5.253%	$191.4447	$191.44	$191.45	$191.40
7 purchase totals =	$829.60		$896.2890	$896.28	$896.30	$896.20