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	$65.29	7.559%	$70.2253	$70.23	$70.25	$70.20
Purchase #2	$134.63	5.556%	$142.11	$142.11	$142.10	$142.10
Purchase #3	$84.96	6.284%	$90.2989	$90.30	$90.30	$90.30
Purchase #4	$200.99	4.233%	$209.4979	$209.50	$209.50	$209.50
Purchase #5	$55.31	11.280%	$61.549	$61.55	$61.55	$61.50
Purchase #6	$7.27	6.675%	$7.7553	$7.76	$7.75	$7.80
Purchase #7	$195.73	11.323%	$217.8925	$217.89	$217.90	$217.90
7 purchase totals =	$744.18		$799.3289	$799.34	$799.35	$799.30