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	$75.48	4.192%	$78.6441	$78.64	$78.65	$78.60
Purchase #2	$182.36	12.847%	$205.7878	$205.79	$205.80	$205.80
Purchase #3	$20.88	4.710%	$21.8634	$21.86	$21.85	$21.90
Purchase #4	$53.43	8.192%	$57.807	$57.81	$57.80	$57.80
Purchase #5	$245.81	3.416%	$254.2069	$254.21	$254.20	$254.20
Purchase #6	$214.72	9.747%	$235.6488	$235.65	$235.65	$235.60
Purchase #7	$211.92	5.333%	$223.2217	$223.22	$223.20	$223.20
7 purchase totals =	$1,004.60		$1,077.1797	$1,077.18	$1,077.15	$1,077.10