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	$213.88	5.152%	$224.8991	$224.90	$224.90	$224.90
Purchase #2	$96.93	13.411%	$109.9293	$109.93	$109.95	$109.90
Purchase #3	$225.98	3.710%	$234.3639	$234.36	$234.35	$234.40
Purchase #4	$33.87	13.354%	$38.393	$38.39	$38.40	$38.40
Purchase #5	$179.97	13.166%	$203.6649	$203.66	$203.65	$203.70
Purchase #6	$211.94	5.422%	$223.4314	$223.43	$223.45	$223.40
Purchase #7	$109.73	6.132%	$116.4586	$116.46	$116.45	$116.50
7 purchase totals =	$1,072.30		$1,151.1402	$1,151.13	$1,151.15	$1,151.20