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	$106.33	5.163%	$111.8198	$111.82	$111.80	$111.80
Purchase #2	$209.88	11.345%	$233.6909	$233.69	$233.70	$233.70
Purchase #3	$38.69	8.607%	$42.02	$42.02	$42.00	$42.00
Purchase #4	$148.67	5.817%	$157.3181	$157.32	$157.30	$157.30
Purchase #5	$246.97	11.173%	$274.564	$274.56	$274.55	$274.60
Purchase #6	$80.75	8.568%	$87.6687	$87.67	$87.65	$87.70
Purchase #7	$119.40	3.421%	$123.4847	$123.48	$123.50	$123.50
7 purchase totals =	$950.69		$1,030.5662	$1,030.56	$1,030.50	$1,030.60