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	$21.89	4.434%	$22.8606	$22.86	$22.85	$22.90
Purchase #2	$47.77	9.174%	$52.1524	$52.15	$52.15	$52.20
Purchase #3	$155.33	3.367%	$160.56	$160.56	$160.55	$160.60
Purchase #4	$231.46	10.539%	$255.8536	$255.85	$255.85	$255.90
Purchase #5	$167.51	4.484%	$175.0211	$175.02	$175.00	$175.00
Purchase #6	$122.44	5.613%	$129.3126	$129.31	$129.30	$129.30
Purchase #7	$196.86	11.397%	$219.2961	$219.30	$219.30	$219.30
7 purchase totals =	$943.26		$1,015.0564	$1,015.05	$1,015.00	$1,015.20