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	$43.37	11.416%	$48.3211	$48.32	$48.30	$48.30
Purchase #2	$132.74	13.751%	$150.9931	$150.99	$151.00	$151.00
Purchase #3	$204.37	6.466%	$217.5846	$217.58	$217.60	$217.60
Purchase #4	$162.71	11.376%	$181.2199	$181.22	$181.20	$181.20
Purchase #5	$54.81	11.497%	$61.1115	$61.11	$61.10	$61.10
Purchase #6	$82.38	9.293%	$90.0356	$90.04	$90.05	$90.00
Purchase #7	$28.95	7.260%	$31.0518	$31.05	$31.05	$31.10
7 purchase totals =	$709.33		$780.3176	$780.31	$780.30	$780.30