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	$148.99	13.670%	$169.3569	$169.36	$169.35	$169.40
Purchase #2	$57.64	13.179%	$65.2364	$65.24	$65.25	$65.20
Purchase #3	$20.36	11.217%	$22.6438	$22.64	$22.65	$22.60
Purchase #4	$66.69	12.112%	$74.7675	$74.77	$74.75	$74.80
Purchase #5	$116.32	9.608%	$127.496	$127.50	$127.50	$127.50
Purchase #6	$148.91	13.363%	$168.8088	$168.81	$168.80	$168.80
Purchase #7	$171.65	12.203%	$192.5964	$192.60	$192.60	$192.60
7 purchase totals =	$730.56		$820.9058	$820.92	$820.90	$820.90