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	$65.89	10.269%	$72.6562	$72.66	$72.65	$72.70
Purchase #2	$180.80	8.274%	$195.7594	$195.76	$195.75	$195.80
Purchase #3	$196.40	7.118%	$210.3798	$210.38	$210.40	$210.40
Purchase #4	$166.25	3.205%	$171.5783	$171.58	$171.60	$171.60
Purchase #5	$164.33	10.498%	$181.5814	$181.58	$181.60	$181.60
Purchase #6	$159.56	8.184%	$172.6184	$172.62	$172.60	$172.60
Purchase #7	$150.55	10.864%	$166.9058	$166.91	$166.90	$166.90
7 purchase totals =	$1,083.78		$1,171.4793	$1,171.49	$1,171.50	$1,171.60