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	$124.27	3.865%	$129.073	$129.07	$129.05	$129.10
Purchase #2	$96.57	3.439%	$99.891	$99.89	$99.90	$99.90
Purchase #3	$42.50	7.538%	$45.7037	$45.70	$45.70	$45.70
Purchase #4	$11.34	13.793%	$12.9041	$12.90	$12.90	$12.90
Purchase #5	$170.81	6.241%	$181.4703	$181.47	$181.45	$181.50
Purchase #6	$213.33	7.407%	$229.1314	$229.13	$229.15	$229.10
Purchase #7	$181.97	4.567%	$190.2806	$190.28	$190.30	$190.30
7 purchase totals =	$840.79		$888.4541	$888.44	$888.45	$888.50