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	$153.89	13.687%	$174.9529	$174.95	$174.95	$175.00
Purchase #2	$179.26	6.480%	$190.876	$190.88	$190.90	$190.90
Purchase #3	$37.88	13.796%	$43.1059	$43.11	$43.10	$43.10
Purchase #4	$159.47	8.666%	$173.2897	$173.29	$173.30	$173.30
Purchase #5	$148.27	3.562%	$153.5514	$153.55	$153.55	$153.60
Purchase #6	$35.71	4.145%	$37.1902	$37.19	$37.20	$37.20
Purchase #7	$95.28	9.214%	$104.0591	$104.06	$104.05	$104.10
7 purchase totals =	$809.76		$877.0252	$877.03	$877.05	$877.20