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	$35.68	3.408%	$36.896	$36.90	$36.90	$36.90
Purchase #2	$64.40	10.356%	$71.0693	$71.07	$71.05	$71.10
Purchase #3	$175.53	10.813%	$194.5101	$194.51	$194.50	$194.50
Purchase #4	$38.91	11.757%	$43.4846	$43.48	$43.50	$43.50
Purchase #5	$191.52	3.515%	$198.2519	$198.25	$198.25	$198.30
Purchase #6	$125.77	12.714%	$141.7604	$141.76	$141.75	$141.80
Purchase #7	$217.80	7.132%	$233.3335	$233.33	$233.35	$233.30
7 purchase totals =	$849.61		$919.3058	$919.30	$919.30	$919.40