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	$125.56	13.846%	$142.945	$142.95	$142.95	$142.90
Purchase #2	$211.87	3.114%	$218.4676	$218.47	$218.45	$218.50
Purchase #3	$120.72	6.764%	$128.8855	$128.89	$128.90	$128.90
Purchase #4	$79.93	4.478%	$83.5093	$83.51	$83.50	$83.50
Purchase #5	$115.76	9.630%	$126.9077	$126.91	$126.90	$126.90
Purchase #6	$96.26	5.286%	$101.3483	$101.35	$101.35	$101.30
Purchase #7	$149.88	3.744%	$155.4915	$155.49	$155.50	$155.50
7 purchase totals =	$899.98		$957.5549	$957.57	$957.55	$957.50