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	$185.67	3.224%	$191.656	$191.66	$191.65	$191.70
Purchase #2	$236.58	12.377%	$265.8615	$265.86	$265.85	$265.90
Purchase #3	$33.86	4.415%	$35.3549	$35.35	$35.35	$35.40
Purchase #4	$134.78	5.104%	$141.6592	$141.66	$141.65	$141.70
Purchase #5	$188.73	3.805%	$195.9112	$195.91	$195.90	$195.90
Purchase #6	$69.93	6.580%	$74.5314	$74.53	$74.55	$74.50
Purchase #7	$195.83	11.557%	$218.4621	$218.46	$218.45	$218.50
7 purchase totals =	$1,045.38		$1,123.4363	$1,123.43	$1,123.40	$1,123.60