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	$88.49	12.168%	$99.2575	$99.26	$99.25	$99.30
Purchase #2	$129.71	8.811%	$141.1387	$141.14	$141.15	$141.10
Purchase #3	$233.39	4.672%	$244.294	$244.29	$244.30	$244.30
Purchase #4	$75.69	12.656%	$85.2693	$85.27	$85.25	$85.30
Purchase #5	$212.45	3.708%	$220.3276	$220.33	$220.35	$220.30
Purchase #6	$114.65	3.109%	$118.2145	$118.21	$118.20	$118.20
Purchase #7	$159.41	7.507%	$171.3769	$171.38	$171.40	$171.40
7 purchase totals =	$1,013.79		$1,079.8785	$1,079.88	$1,079.90	$1,079.90