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	$125.90	5.357%	$132.6445	$132.64	$132.65	$132.60
Purchase #2	$144.69	4.374%	$151.0187	$151.02	$151.00	$151.00
Purchase #3	$167.51	12.861%	$189.0535	$189.05	$189.05	$189.10
Purchase #4	$57.71	12.306%	$64.8118	$64.81	$64.80	$64.80
Purchase #5	$64.51	10.332%	$71.1752	$71.18	$71.20	$71.20
Purchase #6	$233.76	7.139%	$250.4481	$250.45	$250.45	$250.40
Purchase #7	$178.39	6.222%	$189.4894	$189.49	$189.50	$189.50
7 purchase totals =	$972.47		$1,048.6412	$1,048.64	$1,048.65	$1,048.60