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	$129.45	9.562%	$141.828	$141.83	$141.85	$141.80
Purchase #2	$70.83	11.253%	$78.8005	$78.80	$78.80	$78.80
Purchase #3	$233.31	3.356%	$241.1399	$241.14	$241.15	$241.10
Purchase #4	$88.72	4.102%	$92.3593	$92.36	$92.35	$92.40
Purchase #5	$39.99	5.336%	$42.1239	$42.12	$42.10	$42.10
Purchase #6	$186.31	10.616%	$206.0887	$206.09	$206.10	$206.10
Purchase #7	$85.85	6.800%	$91.6878	$91.69	$91.70	$91.70
7 purchase totals =	$834.46		$894.0281	$894.03	$894.05	$894.00