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	$128.91	13.166%	$145.8823	$145.88	$145.90	$145.90
Purchase #2	$156.76	8.393%	$169.9169	$169.92	$169.90	$169.90
Purchase #3	$62.53	8.361%	$67.7581	$67.76	$67.75	$67.80
Purchase #4	$11.70	13.654%	$13.2975	$13.30	$13.30	$13.30
Purchase #5	$116.51	6.262%	$123.8059	$123.81	$123.80	$123.80
Purchase #6	$116.55	12.360%	$130.9556	$130.96	$130.95	$131.00
Purchase #7	$94.29	6.205%	$100.1407	$100.14	$100.15	$100.10
7 purchase totals =	$687.25		$751.7570	$751.77	$751.75	$751.80