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	$89.98	4.555%	$94.0786	$94.08	$94.10	$94.10
Purchase #2	$120.67	5.465%	$127.2646	$127.26	$127.25	$127.30
Purchase #3	$139.38	4.681%	$145.9044	$145.90	$145.90	$145.90
Purchase #4	$60.45	11.696%	$67.5202	$67.52	$67.50	$67.50
Purchase #5	$33.34	11.495%	$37.1724	$37.17	$37.15	$37.20
Purchase #6	$16.62	7.630%	$17.8881	$17.89	$17.90	$17.90
Purchase #7	$68.33	5.573%	$72.138	$72.14	$72.15	$72.10
7 purchase totals =	$528.77		$561.9663	$561.96	$561.95	$562.00