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	$115.46	11.393%	$128.6144	$128.61	$128.60	$128.60
Purchase #2	$12.75	11.813%	$14.2562	$14.26	$14.25	$14.30
Purchase #3	$48.68	5.792%	$51.4995	$51.50	$51.50	$51.50
Purchase #4	$176.68	6.814%	$188.719	$188.72	$188.70	$188.70
Purchase #5	$100.31	7.229%	$107.5614	$107.56	$107.55	$107.60
Purchase #6	$90.33	4.223%	$94.1446	$94.14	$94.15	$94.10
Purchase #7	$24.51	13.132%	$27.7287	$27.73	$27.75	$27.70
7 purchase totals =	$568.72		$612.5238	$612.52	$612.50	$612.50