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	$36.89	13.369%	$41.8218	$41.82	$41.80	$41.80
Purchase #2	$221.44	11.317%	$246.5004	$246.50	$246.50	$246.50
Purchase #3	$147.77	12.578%	$166.3565	$166.36	$166.35	$166.40
Purchase #4	$110.30	9.306%	$120.5645	$120.56	$120.55	$120.60
Purchase #5	$176.47	8.280%	$191.0817	$191.08	$191.10	$191.10
Purchase #6	$62.57	4.553%	$65.4188	$65.42	$65.40	$65.40
Purchase #7	$244.32	11.871%	$273.3232	$273.32	$273.30	$273.30
7 purchase totals =	$999.76		$1,105.0669	$1,105.06	$1,105.00	$1,105.10