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	$198.31	7.333%	$212.8521	$212.85	$212.85	$212.90
Purchase #2	$53.64	11.601%	$59.8628	$59.86	$59.85	$59.90
Purchase #3	$77.81	10.395%	$85.8983	$85.90	$85.90	$85.90
Purchase #4	$178.98	11.478%	$199.5233	$199.52	$199.50	$199.50
Purchase #5	$142.40	3.621%	$147.5563	$147.56	$147.55	$147.60
Purchase #6	$22.54	13.866%	$25.6654	$25.67	$25.65	$25.70
Purchase #7	$217.53	5.632%	$229.7813	$229.78	$229.80	$229.80
7 purchase totals =	$891.21		$961.1395	$961.14	$961.10	$961.30