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	$93.61	5.853%	$99.089	$99.09	$99.10	$99.10
Purchase #2	$108.74	5.128%	$114.3162	$114.32	$114.30	$114.30
Purchase #3	$51.40	11.378%	$57.2483	$57.25	$57.25	$57.20
Purchase #4	$203.61	13.157%	$230.399	$230.40	$230.40	$230.40
Purchase #5	$99.50	7.273%	$106.7366	$106.74	$106.75	$106.70
Purchase #6	$20.91	7.266%	$22.4293	$22.43	$22.45	$22.40
Purchase #7	$98.32	13.138%	$111.2373	$111.24	$111.25	$111.20
7 purchase totals =	$676.09		$741.4557	$741.47	$741.50	$741.30