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	$73.28	11.157%	$81.4558	$81.46	$81.45	$81.50
Purchase #2	$169.80	4.209%	$176.9469	$176.95	$176.95	$176.90
Purchase #3	$127.53	3.412%	$131.8813	$131.88	$131.90	$131.90
Purchase #4	$33.35	12.732%	$37.5961	$37.60	$37.60	$37.60
Purchase #5	$188.92	11.796%	$211.205	$211.21	$211.20	$211.20
Purchase #6	$232.72	4.655%	$243.5531	$243.55	$243.55	$243.60
Purchase #7	$116.60	7.362%	$125.1841	$125.18	$125.20	$125.20
7 purchase totals =	$942.20		$1,007.8223	$1,007.83	$1,007.85	$1,007.90