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	$131.66	12.717%	$148.4032	$148.40	$148.40	$148.40
Purchase #2	$133.70	6.626%	$142.559	$142.56	$142.55	$142.60
Purchase #3	$13.30	11.667%	$14.8517	$14.85	$14.85	$14.90
Purchase #4	$236.89	12.348%	$266.1412	$266.14	$266.15	$266.10
Purchase #5	$238.73	4.699%	$249.9479	$249.95	$249.95	$249.90
Purchase #6	$96.68	9.111%	$105.4885	$105.49	$105.50	$105.50
Purchase #7	$172.61	5.371%	$181.8809	$181.88	$181.90	$181.90
7 purchase totals =	$1,023.57		$1,109.2724	$1,109.27	$1,109.30	$1,109.30