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	$114.34	4.678%	$119.6888	$119.69	$119.70	$119.70
Purchase #2	$202.95	4.244%	$211.5632	$211.56	$211.55	$211.60
Purchase #3	$169.40	11.261%	$188.4761	$188.48	$188.50	$188.50
Purchase #4	$214.65	11.134%	$238.5491	$238.55	$238.55	$238.50
Purchase #5	$66.43	12.778%	$74.9184	$74.92	$74.90	$74.90
Purchase #6	$115.33	11.598%	$128.706	$128.71	$128.70	$128.70
Purchase #7	$118.56	7.671%	$127.6547	$127.65	$127.65	$127.70
7 purchase totals =	$1,001.66		$1,089.5563	$1,089.56	$1,089.55	$1,089.60