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	$129.71	10.740%	$143.6409	$143.64	$143.65	$143.60
Purchase #2	$101.87	5.361%	$107.3313	$107.33	$107.35	$107.30
Purchase #3	$96.94	3.371%	$100.2078	$100.21	$100.20	$100.20
Purchase #4	$55.35	5.633%	$58.4679	$58.47	$58.45	$58.50
Purchase #5	$236.78	11.799%	$264.7177	$264.72	$264.70	$264.70
Purchase #6	$233.82	8.842%	$254.4944	$254.49	$254.50	$254.50
Purchase #7	$198.78	12.481%	$223.5897	$223.59	$223.60	$223.60
7 purchase totals =	$1,053.25		$1,152.4497	$1,152.45	$1,152.45	$1,152.40