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	$76.51	3.740%	$79.3715	$79.37	$79.35	$79.40
Purchase #2	$112.62	13.382%	$127.6908	$127.69	$127.70	$127.70
Purchase #3	$175.81	5.725%	$185.8751	$185.88	$185.90	$185.90
Purchase #4	$229.82	12.374%	$258.2579	$258.26	$258.25	$258.30
Purchase #5	$149.50	11.191%	$166.2305	$166.23	$166.25	$166.20
Purchase #6	$202.67	6.807%	$216.4657	$216.47	$216.45	$216.50
Purchase #7	$79.27	7.619%	$85.3096	$85.31	$85.30	$85.30
7 purchase totals =	$1,026.20		$1,119.2011	$1,119.21	$1,119.20	$1,119.30