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	$200.41	11.405%	$223.2668	$223.27	$223.25	$223.30
Purchase #2	$179.82	6.764%	$191.983	$191.98	$192.00	$192.00
Purchase #3	$172.40	13.689%	$195.9998	$196.00	$196.00	$196.00
Purchase #4	$211.27	5.295%	$222.4567	$222.46	$222.45	$222.50
Purchase #5	$157.93	11.253%	$175.7019	$175.70	$175.70	$175.70
Purchase #6	$197.63	12.318%	$221.9741	$221.97	$221.95	$222.00
Purchase #7	$29.38	10.722%	$32.5301	$32.53	$32.55	$32.50
7 purchase totals =	$1,148.84		$1,263.9124	$1,263.91	$1,263.90	$1,264.00