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	$172.74	8.442%	$187.3227	$187.32	$187.30	$187.30
Purchase #2	$47.53	6.294%	$50.5215	$50.52	$50.50	$50.50
Purchase #3	$18.87	11.581%	$21.0553	$21.06	$21.05	$21.10
Purchase #4	$176.81	7.354%	$189.8126	$189.81	$189.80	$189.80
Purchase #5	$172.47	8.694%	$187.4645	$187.46	$187.45	$187.50
Purchase #6	$154.35	7.490%	$165.9108	$165.91	$165.90	$165.90
Purchase #7	$238.77	10.169%	$263.0505	$263.05	$263.05	$263.10
7 purchase totals =	$981.54		$1,065.1379	$1,065.13	$1,065.05	$1,065.20