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	$234.30	4.743%	$245.4128	$245.41	$245.40	$245.40
Purchase #2	$57.25	4.599%	$59.8829	$59.88	$59.90	$59.90
Purchase #3	$55.79	9.763%	$61.2368	$61.24	$61.25	$61.20
Purchase #4	$15.69	9.764%	$17.222	$17.22	$17.20	$17.20
Purchase #5	$209.25	6.642%	$223.1484	$223.15	$223.15	$223.10
Purchase #6	$93.89	7.294%	$100.7383	$100.74	$100.75	$100.70
Purchase #7	$162.36	9.187%	$177.276	$177.28	$177.30	$177.30
7 purchase totals =	$828.53		$884.9172	$884.92	$884.95	$884.80