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	$242.59	4.474%	$253.4435	$253.44	$253.45	$253.40
Purchase #2	$73.34	10.297%	$80.8918	$80.89	$80.90	$80.90
Purchase #3	$181.28	5.283%	$190.857	$190.86	$190.85	$190.90
Purchase #4	$157.63	5.141%	$165.7338	$165.73	$165.75	$165.70
Purchase #5	$16.68	6.352%	$17.7395	$17.74	$17.75	$17.70
Purchase #6	$222.68	3.409%	$230.2712	$230.27	$230.25	$230.30
Purchase #7	$69.37	12.486%	$78.0315	$78.03	$78.05	$78.00
7 purchase totals =	$963.57		$1,016.9683	$1,016.96	$1,017.00	$1,016.90