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	$174.33	12.754%	$196.564	$196.56	$196.55	$196.60
Purchase #2	$114.25	10.735%	$126.5147	$126.51	$126.50	$126.50
Purchase #3	$48.83	13.392%	$55.3693	$55.37	$55.35	$55.40
Purchase #4	$133.73	12.438%	$150.3633	$150.36	$150.35	$150.40
Purchase #5	$95.38	6.650%	$101.7228	$101.72	$101.70	$101.70
Purchase #6	$193.64	10.372%	$213.7243	$213.72	$213.70	$213.70
Purchase #7	$243.60	11.349%	$271.2462	$271.25	$271.25	$271.20
7 purchase totals =	$1,003.76		$1,115.5046	$1,115.49	$1,115.40	$1,115.50