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	$53.50	12.585%	$60.233	$60.23	$60.25	$60.20
Purchase #2	$86.74	11.706%	$96.8938	$96.89	$96.90	$96.90
Purchase #3	$155.81	12.236%	$174.8749	$174.87	$174.85	$174.90
Purchase #4	$95.56	8.199%	$103.395	$103.40	$103.40	$103.40
Purchase #5	$175.41	8.544%	$190.397	$190.40	$190.40	$190.40
Purchase #6	$137.28	4.826%	$143.9051	$143.91	$143.90	$143.90
Purchase #7	$206.71	11.674%	$230.8413	$230.84	$230.85	$230.80
7 purchase totals =	$911.01		$1,000.5401	$1,000.54	$1,000.55	$1,000.50