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	$56.59	5.701%	$59.8162	$59.82	$59.80	$59.80
Purchase #2	$142.59	4.755%	$149.3702	$149.37	$149.35	$149.40
Purchase #3	$229.36	7.174%	$245.8143	$245.81	$245.80	$245.80
Purchase #4	$246.47	7.821%	$265.7464	$265.75	$265.75	$265.70
Purchase #5	$225.68	4.145%	$235.0344	$235.03	$235.05	$235.00
Purchase #6	$18.86	7.363%	$20.2487	$20.25	$20.25	$20.20
Purchase #7	$78.74	9.798%	$86.4549	$86.45	$86.45	$86.50
7 purchase totals =	$998.29		$1,062.4851	$1,062.48	$1,062.45	$1,062.40