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	$172.33	7.445%	$185.16	$185.16	$185.15	$185.20
Purchase #2	$53.37	11.153%	$59.3224	$59.32	$59.30	$59.30
Purchase #3	$229.50	13.150%	$259.6793	$259.68	$259.70	$259.70
Purchase #4	$135.49	5.608%	$143.0883	$143.09	$143.10	$143.10
Purchase #5	$166.95	4.280%	$174.0955	$174.10	$174.10	$174.10
Purchase #6	$58.35	7.782%	$62.8908	$62.89	$62.90	$62.90
Purchase #7	$105.88	5.511%	$111.715	$111.72	$111.70	$111.70
7 purchase totals =	$921.87		$995.9513	$995.96	$995.95	$996.00