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	$68.96	7.109%	$73.8624	$73.86	$73.85	$73.90
Purchase #2	$176.59	6.490%	$188.0507	$188.05	$188.05	$188.10
Purchase #3	$138.51	12.552%	$155.8958	$155.90	$155.90	$155.90
Purchase #4	$184.59	13.419%	$209.3601	$209.36	$209.35	$209.40
Purchase #5	$80.93	3.292%	$83.5942	$83.59	$83.60	$83.60
Purchase #6	$101.32	3.143%	$104.5045	$104.50	$104.50	$104.50
Purchase #7	$55.27	3.846%	$57.3957	$57.40	$57.40	$57.40
7 purchase totals =	$806.17		$872.6634	$872.66	$872.65	$872.80