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	$208.89	3.205%	$215.5849	$215.58	$215.60	$215.60
Purchase #2	$93.70	6.102%	$99.4176	$99.42	$99.40	$99.40
Purchase #3	$173.89	4.452%	$181.6316	$181.63	$181.65	$181.60
Purchase #4	$243.36	9.264%	$265.9049	$265.90	$265.90	$265.90
Purchase #5	$47.62	9.842%	$52.3068	$52.31	$52.30	$52.30
Purchase #6	$193.60	13.655%	$220.0361	$220.04	$220.05	$220.00
Purchase #7	$24.89	13.870%	$28.3422	$28.34	$28.35	$28.30
7 purchase totals =	$985.95		$1,063.2241	$1,063.22	$1,063.25	$1,063.10