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	$137.32	9.393%	$150.2185	$150.22	$150.20	$150.20
Purchase #2	$147.62	3.424%	$152.6745	$152.67	$152.65	$152.70
Purchase #3	$56.48	4.815%	$59.1995	$59.20	$59.20	$59.20
Purchase #4	$111.81	4.378%	$116.705	$116.71	$116.70	$116.70
Purchase #5	$28.25	5.150%	$29.7049	$29.70	$29.70	$29.70
Purchase #6	$91.61	3.466%	$94.7852	$94.79	$94.80	$94.80
Purchase #7	$123.31	6.371%	$131.1661	$131.17	$131.15	$131.20
7 purchase totals =	$696.40		$734.4537	$734.46	$734.40	$734.50