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	$105.40	10.553%	$116.5229	$116.52	$116.50	$116.50
Purchase #2	$72.74	3.433%	$75.2372	$75.24	$75.25	$75.20
Purchase #3	$94.39	5.847%	$99.909	$99.91	$99.90	$99.90
Purchase #4	$70.64	10.469%	$78.0353	$78.04	$78.05	$78.00
Purchase #5	$74.47	4.272%	$77.6514	$77.65	$77.65	$77.70
Purchase #6	$189.44	3.667%	$196.3868	$196.39	$196.40	$196.40
Purchase #7	$211.87	8.682%	$230.2646	$230.26	$230.25	$230.30
7 purchase totals =	$818.95		$874.0072	$874.01	$874.00	$874.00