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	$84.65	13.484%	$96.0642	$96.06	$96.05	$96.10
Purchase #2	$152.65	9.282%	$166.819	$166.82	$166.80	$166.80
Purchase #3	$169.40	7.209%	$181.612	$181.61	$181.60	$181.60
Purchase #4	$175.71	11.851%	$196.5334	$196.53	$196.55	$196.50
Purchase #5	$150.66	5.754%	$159.329	$159.33	$159.35	$159.30
Purchase #6	$45.70	4.787%	$47.8877	$47.89	$47.90	$47.90
Purchase #7	$138.91	11.214%	$154.4874	$154.49	$154.50	$154.50
7 purchase totals =	$917.68		$1,002.7327	$1,002.73	$1,002.75	$1,002.70