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	$30.96	11.425%	$34.4972	$34.50	$34.50	$34.50
Purchase #2	$70.56	10.754%	$78.148	$78.15	$78.15	$78.10
Purchase #3	$186.44	5.369%	$196.45	$196.45	$196.45	$196.50
Purchase #4	$151.45	3.163%	$156.2404	$156.24	$156.25	$156.20
Purchase #5	$59.39	3.410%	$61.4152	$61.42	$61.40	$61.40
Purchase #6	$165.76	11.755%	$185.2451	$185.25	$185.25	$185.20
Purchase #7	$179.38	9.154%	$195.8004	$195.80	$195.80	$195.80
7 purchase totals =	$843.94		$907.7963	$907.81	$907.80	$907.70