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	$50.98	7.493%	$54.7999	$54.80	$54.80	$54.80
Purchase #2	$202.44	11.491%	$225.7024	$225.70	$225.70	$225.70
Purchase #3	$181.34	5.266%	$190.8894	$190.89	$190.90	$190.90
Purchase #4	$171.90	4.637%	$179.871	$179.87	$179.85	$179.90
Purchase #5	$61.29	7.408%	$65.8304	$65.83	$65.85	$65.80
Purchase #6	$155.75	4.410%	$162.6186	$162.62	$162.60	$162.60
Purchase #7	$152.64	9.813%	$167.6186	$167.62	$167.60	$167.60
7 purchase totals =	$976.34		$1,047.3303	$1,047.33	$1,047.30	$1,047.30