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	$73.89	11.383%	$82.3009	$82.30	$82.30	$82.30
Purchase #2	$229.39	13.525%	$260.415	$260.42	$260.40	$260.40
Purchase #3	$183.48	13.149%	$207.6058	$207.61	$207.60	$207.60
Purchase #4	$114.56	11.486%	$127.7184	$127.72	$127.70	$127.70
Purchase #5	$192.55	8.795%	$209.4848	$209.48	$209.50	$209.50
Purchase #6	$24.98	5.458%	$26.3434	$26.34	$26.35	$26.30
Purchase #7	$180.90	10.858%	$200.5421	$200.54	$200.55	$200.50
7 purchase totals =	$999.75		$1,114.4104	$1,114.41	$1,114.40	$1,114.30