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	$147.53	8.780%	$160.4831	$160.48	$160.50	$160.50
Purchase #2	$204.54	3.394%	$211.4821	$211.48	$211.50	$211.50
Purchase #3	$113.39	6.287%	$120.5188	$120.52	$120.50	$120.50
Purchase #4	$156.84	10.337%	$173.0526	$173.05	$173.05	$173.10
Purchase #5	$142.44	8.500%	$154.5474	$154.55	$154.55	$154.50
Purchase #6	$170.74	10.298%	$188.3228	$188.32	$188.30	$188.30
Purchase #7	$62.86	6.314%	$66.829	$66.83	$66.85	$66.80
7 purchase totals =	$998.34		$1,075.2358	$1,075.23	$1,075.25	$1,075.20