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	$148.31	13.213%	$167.9062	$167.91	$167.90	$167.90
Purchase #2	$186.26	9.228%	$203.4481	$203.45	$203.45	$203.40
Purchase #3	$166.28	11.662%	$185.6716	$185.67	$185.65	$185.70
Purchase #4	$142.72	6.777%	$152.3921	$152.39	$152.40	$152.40
Purchase #5	$19.70	12.284%	$22.1199	$22.12	$22.10	$22.10
Purchase #6	$233.92	4.263%	$243.892	$243.89	$243.90	$243.90
Purchase #7	$79.34	3.173%	$81.8575	$81.86	$81.85	$81.90
7 purchase totals =	$976.53		$1,057.2874	$1,057.29	$1,057.25	$1,057.30