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	$195.30	10.291%	$215.3983	$215.40	$215.40	$215.40
Purchase #2	$99.38	10.450%	$109.7652	$109.77	$109.75	$109.80
Purchase #3	$222.76	13.760%	$253.4118	$253.41	$253.40	$253.40
Purchase #4	$222.87	11.417%	$248.3151	$248.32	$248.30	$248.30
Purchase #5	$156.75	10.806%	$173.6884	$173.69	$173.70	$173.70
Purchase #6	$68.88	4.210%	$71.7798	$71.78	$71.80	$71.80
Purchase #7	$238.43	9.301%	$260.6064	$260.61	$260.60	$260.60
7 purchase totals =	$1,204.37		$1,332.9650	$1,332.98	$1,332.95	$1,333.00