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	$159.33	13.427%	$180.7232	$180.72	$180.70	$180.70
Purchase #2	$82.28	10.429%	$90.861	$90.86	$90.85	$90.90
Purchase #3	$243.29	8.380%	$263.6777	$263.68	$263.70	$263.70
Purchase #4	$82.51	8.860%	$89.8204	$89.82	$89.80	$89.80
Purchase #5	$120.34	8.185%	$130.1898	$130.19	$130.20	$130.20
Purchase #6	$144.32	11.760%	$161.292	$161.29	$161.30	$161.30
Purchase #7	$48.26	8.332%	$52.281	$52.28	$52.30	$52.30
7 purchase totals =	$880.33		$968.8451	$968.84	$968.85	$968.90