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	$145.50	9.589%	$159.452	$159.45	$159.45	$159.50
Purchase #2	$240.31	7.518%	$258.3765	$258.38	$258.40	$258.40
Purchase #3	$105.80	5.611%	$111.7364	$111.74	$111.75	$111.70
Purchase #4	$102.44	8.728%	$111.381	$111.38	$111.40	$111.40
Purchase #5	$186.49	13.357%	$211.3995	$211.40	$211.40	$211.40
Purchase #6	$73.93	7.148%	$79.2145	$79.21	$79.20	$79.20
Purchase #7	$156.81	3.478%	$162.2639	$162.26	$162.25	$162.30
7 purchase totals =	$1,011.28		$1,093.8238	$1,093.82	$1,093.85	$1,093.90