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	$129.99	13.640%	$147.7206	$147.72	$147.70	$147.70
Purchase #2	$139.46	6.108%	$147.9782	$147.98	$148.00	$148.00
Purchase #3	$120.99	5.455%	$127.59	$127.59	$127.60	$127.60
Purchase #4	$10.85	11.837%	$12.1343	$12.13	$12.15	$12.10
Purchase #5	$96.33	11.229%	$107.1469	$107.15	$107.15	$107.10
Purchase #6	$27.98	13.753%	$31.8281	$31.83	$31.85	$31.80
Purchase #7	$39.86	13.155%	$45.1036	$45.10	$45.10	$45.10
7 purchase totals =	$565.46		$619.5017	$619.50	$619.55	$619.40