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	$164.56	10.286%	$181.4866	$181.49	$181.50	$181.50
Purchase #2	$135.48	7.843%	$146.1057	$146.11	$146.10	$146.10
Purchase #3	$89.77	11.789%	$100.353	$100.35	$100.35	$100.40
Purchase #4	$60.87	10.607%	$67.3265	$67.33	$67.35	$67.30
Purchase #5	$250.85	8.238%	$271.515	$271.52	$271.50	$271.50
Purchase #6	$64.29	10.394%	$70.9723	$70.97	$70.95	$71.00
Purchase #7	$163.90	11.112%	$182.1126	$182.11	$182.10	$182.10
7 purchase totals =	$929.72		$1,019.8717	$1,019.88	$1,019.85	$1,019.90