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	$227.35	7.112%	$243.5191	$243.52	$243.50	$243.50
Purchase #2	$55.39	9.144%	$60.4549	$60.45	$60.45	$60.50
Purchase #3	$30.85	11.292%	$34.3336	$34.33	$34.35	$34.30
Purchase #4	$99.92	3.433%	$103.3503	$103.35	$103.35	$103.40
Purchase #5	$31.44	7.568%	$33.8194	$33.82	$33.80	$33.80
Purchase #6	$89.67	8.470%	$97.265	$97.27	$97.25	$97.30
Purchase #7	$133.30	9.114%	$145.449	$145.45	$145.45	$145.40
7 purchase totals =	$667.92		$718.1913	$718.19	$718.15	$718.20