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	$179.50	9.277%	$196.1522	$196.15	$196.15	$196.20
Purchase #2	$28.46	12.229%	$31.9404	$31.94	$31.95	$31.90
Purchase #3	$91.41	9.689%	$100.2667	$100.27	$100.25	$100.30
Purchase #4	$168.33	4.192%	$175.3864	$175.39	$175.40	$175.40
Purchase #5	$85.77	4.317%	$89.4727	$89.47	$89.45	$89.50
Purchase #6	$144.98	5.206%	$152.5277	$152.53	$152.55	$152.50
Purchase #7	$143.32	10.517%	$158.393	$158.39	$158.40	$158.40
7 purchase totals =	$841.77		$904.1391	$904.14	$904.15	$904.20