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	$50.77	3.297%	$52.4439	$52.44	$52.45	$52.40
Purchase #2	$93.61	3.275%	$96.6757	$96.68	$96.70	$96.70
Purchase #3	$105.49	3.361%	$109.0355	$109.04	$109.05	$109.00
Purchase #4	$87.29	12.576%	$98.2676	$98.27	$98.25	$98.30
Purchase #5	$209.70	3.592%	$217.2324	$217.23	$217.25	$217.20
Purchase #6	$215.64	3.625%	$223.457	$223.46	$223.45	$223.50
Purchase #7	$175.51	6.740%	$187.3394	$187.34	$187.35	$187.30
7 purchase totals =	$938.01		$984.4515	$984.46	$984.50	$984.40