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	$54.74	4.133%	$57.0024	$57.00	$57.00	$57.00
Purchase #2	$91.95	4.146%	$95.7622	$95.76	$95.75	$95.80
Purchase #3	$18.59	13.269%	$21.0567	$21.06	$21.05	$21.10
Purchase #4	$201.52	5.604%	$212.8132	$212.81	$212.80	$212.80
Purchase #5	$48.65	13.196%	$55.0699	$55.07	$55.05	$55.10
Purchase #6	$60.46	7.530%	$65.0126	$65.01	$65.00	$65.00
Purchase #7	$60.41	11.770%	$67.5203	$67.52	$67.50	$67.50
7 purchase totals =	$536.32		$574.2373	$574.23	$574.15	$574.30