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	$69.63	4.519%	$72.7766	$72.78	$72.80	$72.80
Purchase #2	$24.26	5.283%	$25.5417	$25.54	$25.55	$25.50
Purchase #3	$151.45	10.130%	$166.7919	$166.79	$166.80	$166.80
Purchase #4	$131.86	5.678%	$139.347	$139.35	$139.35	$139.30
Purchase #5	$15.37	6.373%	$16.3495	$16.35	$16.35	$16.30
Purchase #6	$203.61	12.599%	$229.2628	$229.26	$229.25	$229.30
Purchase #7	$109.87	12.370%	$123.4609	$123.46	$123.45	$123.50
7 purchase totals =	$706.05		$773.5304	$773.53	$773.55	$773.50