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	$19.61	5.834%	$20.754	$20.75	$20.75	$20.80
Purchase #2	$52.79	7.472%	$56.7345	$56.73	$56.75	$56.70
Purchase #3	$201.74	11.137%	$224.2078	$224.21	$224.20	$224.20
Purchase #4	$225.88	5.488%	$238.2763	$238.28	$238.30	$238.30
Purchase #5	$212.96	13.263%	$241.2049	$241.20	$241.20	$241.20
Purchase #6	$125.46	4.274%	$130.8222	$130.82	$130.80	$130.80
Purchase #7	$215.42	10.663%	$238.3902	$238.39	$238.40	$238.40
7 purchase totals =	$1,053.86		$1,150.3899	$1,150.38	$1,150.40	$1,150.40