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	$133.61	6.637%	$142.4777	$142.48	$142.50	$142.50
Purchase #2	$138.74	12.554%	$156.1574	$156.16	$156.15	$156.20
Purchase #3	$70.90	4.700%	$74.2323	$74.23	$74.25	$74.20
Purchase #4	$78.26	4.774%	$81.9961	$82.00	$82.00	$82.00
Purchase #5	$143.35	9.481%	$156.941	$156.94	$156.95	$156.90
Purchase #6	$155.87	6.113%	$165.3983	$165.40	$165.40	$165.40
Purchase #7	$225.38	10.667%	$249.4213	$249.42	$249.40	$249.40
7 purchase totals =	$946.11		$1,026.6241	$1,026.63	$1,026.65	$1,026.60