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	$203.40	4.731%	$213.0229	$213.02	$213.00	$213.00
Purchase #2	$156.38	9.679%	$171.516	$171.52	$171.50	$171.50
Purchase #3	$31.42	6.453%	$33.4475	$33.45	$33.45	$33.40
Purchase #4	$212.95	7.313%	$228.523	$228.52	$228.50	$228.50
Purchase #5	$36.64	12.585%	$41.2511	$41.25	$41.25	$41.30
Purchase #6	$168.28	7.482%	$180.8707	$180.87	$180.85	$180.90
Purchase #7	$162.84	9.793%	$178.7869	$178.79	$178.80	$178.80
7 purchase totals =	$971.91		$1,047.4181	$1,047.42	$1,047.35	$1,047.40