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	$92.26	6.830%	$98.5614	$98.56	$98.55	$98.60
Purchase #2	$27.91	9.272%	$30.4978	$30.50	$30.50	$30.50
Purchase #3	$212.90	11.827%	$238.0797	$238.08	$238.10	$238.10
Purchase #4	$244.73	6.849%	$261.4916	$261.49	$261.50	$261.50
Purchase #5	$203.45	9.160%	$222.086	$222.09	$222.10	$222.10
Purchase #6	$105.28	6.113%	$111.7158	$111.72	$111.70	$111.70
Purchase #7	$249.40	4.198%	$259.8698	$259.87	$259.85	$259.90
7 purchase totals =	$1,135.93		$1,222.3021	$1,222.31	$1,222.30	$1,222.40