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	$83.29	6.543%	$88.7397	$88.74	$88.75	$88.70
Purchase #2	$168.69	10.384%	$186.2068	$186.21	$186.20	$186.20
Purchase #3	$104.66	4.370%	$109.2336	$109.23	$109.25	$109.20
Purchase #4	$30.46	7.379%	$32.7076	$32.71	$32.70	$32.70
Purchase #5	$54.42	13.741%	$61.8979	$61.90	$61.90	$61.90
Purchase #6	$161.88	6.139%	$171.8178	$171.82	$171.80	$171.80
Purchase #7	$48.88	13.448%	$55.4534	$55.45	$55.45	$55.50
7 purchase totals =	$652.28		$706.0568	$706.06	$706.05	$706.00