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	$107.59	4.173%	$112.0797	$112.08	$112.10	$112.10
Purchase #2	$11.57	5.309%	$12.1843	$12.18	$12.20	$12.20
Purchase #3	$131.90	11.729%	$147.3706	$147.37	$147.35	$147.40
Purchase #4	$114.72	7.225%	$123.0085	$123.01	$123.00	$123.00
Purchase #5	$139.43	5.576%	$147.2046	$147.20	$147.20	$147.20
Purchase #6	$75.50	9.331%	$82.5449	$82.54	$82.55	$82.50
Purchase #7	$153.47	4.192%	$159.9035	$159.90	$159.90	$159.90
7 purchase totals =	$734.18		$784.2961	$784.28	$784.30	$784.30