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	$195.34	7.118%	$209.2443	$209.24	$209.25	$209.20
Purchase #2	$68.33	4.547%	$71.437	$71.44	$71.45	$71.40
Purchase #3	$147.41	12.275%	$165.5046	$165.50	$165.50	$165.50
Purchase #4	$164.98	5.289%	$173.7058	$173.71	$173.70	$173.70
Purchase #5	$86.62	11.674%	$96.732	$96.73	$96.75	$96.70
Purchase #6	$9.83	6.256%	$10.445	$10.45	$10.45	$10.40
Purchase #7	$69.79	3.492%	$72.2271	$72.23	$72.25	$72.20
7 purchase totals =	$742.30		$799.2958	$799.30	$799.35	$799.10