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	$124.42	12.702%	$140.2238	$140.22	$140.20	$140.20
Purchase #2	$212.91	4.486%	$222.4611	$222.46	$222.45	$222.50
Purchase #3	$82.76	12.623%	$93.2068	$93.21	$93.20	$93.20
Purchase #4	$98.94	13.622%	$112.4176	$112.42	$112.40	$112.40
Purchase #5	$148.57	12.278%	$166.8114	$166.81	$166.80	$166.80
Purchase #6	$249.91	12.631%	$281.4761	$281.48	$281.50	$281.50
Purchase #7	$136.28	11.457%	$151.8936	$151.89	$151.90	$151.90
7 purchase totals =	$1,053.79		$1,168.4904	$1,168.49	$1,168.45	$1,168.50