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	$144.59	11.199%	$160.7826	$160.78	$160.80	$160.80
Purchase #2	$49.92	11.517%	$55.6693	$55.67	$55.65	$55.70
Purchase #3	$222.49	9.323%	$243.2327	$243.23	$243.25	$243.20
Purchase #4	$73.71	12.554%	$82.9636	$82.96	$82.95	$83.00
Purchase #5	$141.44	6.128%	$150.1074	$150.11	$150.10	$150.10
Purchase #6	$122.60	4.364%	$127.9503	$127.95	$127.95	$128.00
Purchase #7	$200.87	4.852%	$210.6162	$210.62	$210.60	$210.60
7 purchase totals =	$955.62		$1,031.3221	$1,031.32	$1,031.30	$1,031.40