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	$94.56	13.481%	$107.3076	$107.31	$107.30	$107.30
Purchase #2	$69.51	3.669%	$72.0603	$72.06	$72.05	$72.10
Purchase #3	$27.96	13.516%	$31.7391	$31.74	$31.75	$31.70
Purchase #4	$50.86	11.232%	$56.5726	$56.57	$56.55	$56.60
Purchase #5	$219.81	12.453%	$247.1829	$247.18	$247.20	$247.20
Purchase #6	$58.84	4.612%	$61.5537	$61.55	$61.55	$61.60
Purchase #7	$164.25	4.654%	$171.8942	$171.89	$171.90	$171.90
7 purchase totals =	$685.79		$748.3104	$748.30	$748.30	$748.40