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	$171.27	8.140%	$185.2114	$185.21	$185.20	$185.20
Purchase #2	$95.71	12.728%	$107.892	$107.89	$107.90	$107.90
Purchase #3	$240.71	9.173%	$262.7903	$262.79	$262.80	$262.80
Purchase #4	$147.59	12.786%	$166.4609	$166.46	$166.45	$166.50
Purchase #5	$222.41	5.307%	$234.2133	$234.21	$234.20	$234.20
Purchase #6	$72.31	9.799%	$79.3957	$79.40	$79.40	$79.40
Purchase #7	$48.64	3.349%	$50.269	$50.27	$50.25	$50.30
7 purchase totals =	$998.64		$1,086.2326	$1,086.23	$1,086.20	$1,086.30