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	$163.60	5.679%	$172.8908	$172.89	$172.90	$172.90
Purchase #2	$187.97	9.238%	$205.3347	$205.33	$205.35	$205.30
Purchase #3	$118.88	4.721%	$124.4923	$124.49	$124.50	$124.50
Purchase #4	$191.71	10.741%	$212.3016	$212.30	$212.30	$212.30
Purchase #5	$72.78	12.535%	$81.903	$81.90	$81.90	$81.90
Purchase #6	$246.74	11.765%	$275.769	$275.77	$275.75	$275.80
Purchase #7	$165.63	11.180%	$184.1474	$184.15	$184.15	$184.10
7 purchase totals =	$1,147.31		$1,256.8388	$1,256.83	$1,256.85	$1,256.80