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	$171.73	8.350%	$186.0695	$186.07	$186.05	$186.10
Purchase #2	$40.58	4.192%	$42.2811	$42.28	$42.30	$42.30
Purchase #3	$88.49	5.547%	$93.3985	$93.40	$93.40	$93.40
Purchase #4	$230.46	12.127%	$258.4079	$258.41	$258.40	$258.40
Purchase #5	$205.79	7.740%	$221.7181	$221.72	$221.70	$221.70
Purchase #6	$230.65	10.691%	$255.3088	$255.31	$255.30	$255.30
Purchase #7	$92.67	13.723%	$105.3871	$105.39	$105.40	$105.40
7 purchase totals =	$1,060.37		$1,162.5710	$1,162.58	$1,162.55	$1,162.60