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	$10.55	7.590%	$11.3507	$11.35	$11.35	$11.40
Purchase #2	$64.72	8.784%	$70.405	$70.41	$70.40	$70.40
Purchase #3	$120.45	3.223%	$124.3321	$124.33	$124.35	$124.30
Purchase #4	$177.37	7.857%	$191.306	$191.31	$191.30	$191.30
Purchase #5	$80.83	10.811%	$89.5685	$89.57	$89.55	$89.60
Purchase #6	$202.88	9.183%	$221.5105	$221.51	$221.50	$221.50
Purchase #7	$111.48	4.346%	$116.3249	$116.32	$116.30	$116.30
7 purchase totals =	$768.28		$824.7977	$824.80	$824.75	$824.80