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	$172.96	12.113%	$193.9106	$193.91	$193.90	$193.90
Purchase #2	$31.72	4.520%	$33.1537	$33.15	$33.15	$33.20
Purchase #3	$206.49	4.743%	$216.2838	$216.28	$216.30	$216.30
Purchase #4	$135.27	5.364%	$142.5259	$142.53	$142.55	$142.50
Purchase #5	$187.84	10.866%	$208.2507	$208.25	$208.25	$208.30
Purchase #6	$55.71	4.852%	$58.413	$58.41	$58.40	$58.40
Purchase #7	$233.75	7.258%	$250.7156	$250.72	$250.70	$250.70
7 purchase totals =	$1,023.74		$1,103.2533	$1,103.25	$1,103.25	$1,103.30