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	$199.55	8.157%	$215.8273	$215.83	$215.85	$215.80
Purchase #2	$208.90	12.443%	$234.8934	$234.89	$234.90	$234.90
Purchase #3	$188.72	10.787%	$209.0772	$209.08	$209.10	$209.10
Purchase #4	$91.54	9.152%	$99.9177	$99.92	$99.90	$99.90
Purchase #5	$180.88	6.434%	$192.5178	$192.52	$192.50	$192.50
Purchase #6	$120.46	5.709%	$127.3371	$127.34	$127.35	$127.30
Purchase #7	$172.90	9.394%	$189.1422	$189.14	$189.15	$189.10
7 purchase totals =	$1,162.95		$1,268.7127	$1,268.72	$1,268.75	$1,268.60