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	$184.84	3.401%	$191.1264	$191.13	$191.15	$191.10
Purchase #2	$97.73	6.470%	$104.0531	$104.05	$104.05	$104.10
Purchase #3	$208.56	12.787%	$235.2286	$235.23	$235.25	$235.20
Purchase #4	$116.90	12.490%	$131.5008	$131.50	$131.50	$131.50
Purchase #5	$87.61	5.624%	$92.5372	$92.54	$92.55	$92.50
Purchase #6	$245.81	12.563%	$276.6911	$276.69	$276.70	$276.70
Purchase #7	$37.86	9.129%	$41.3162	$41.32	$41.30	$41.30
7 purchase totals =	$979.31		$1,072.4534	$1,072.46	$1,072.50	$1,072.40