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	$148.98	10.444%	$164.5395	$164.54	$164.55	$164.50
Purchase #2	$200.82	5.520%	$211.9053	$211.91	$211.90	$211.90
Purchase #3	$99.38	5.445%	$104.7912	$104.79	$104.80	$104.80
Purchase #4	$78.53	13.859%	$89.4135	$89.41	$89.40	$89.40
Purchase #5	$234.28	11.773%	$261.8618	$261.86	$261.85	$261.90
Purchase #6	$25.53	13.231%	$28.9079	$28.91	$28.90	$28.90
Purchase #7	$46.90	4.195%	$48.8675	$48.87	$48.85	$48.90
7 purchase totals =	$834.42		$910.2867	$910.29	$910.25	$910.30