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	$182.73	3.499%	$189.1237	$189.12	$189.10	$189.10
Purchase #2	$240.66	7.371%	$258.399	$258.40	$258.40	$258.40
Purchase #3	$119.69	6.501%	$127.471	$127.47	$127.45	$127.50
Purchase #4	$227.98	8.596%	$247.5772	$247.58	$247.60	$247.60
Purchase #5	$163.66	6.402%	$174.1375	$174.14	$174.15	$174.10
Purchase #6	$232.46	9.747%	$255.1179	$255.12	$255.10	$255.10
Purchase #7	$65.97	8.711%	$71.7166	$71.72	$71.70	$71.70
7 purchase totals =	$1,233.15		$1,323.5429	$1,323.55	$1,323.50	$1,323.50