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	$163.72	13.627%	$186.0301	$186.03	$186.05	$186.00
Purchase #2	$98.56	6.336%	$104.8048	$104.80	$104.80	$104.80
Purchase #3	$50.61	9.811%	$55.5753	$55.58	$55.60	$55.60
Purchase #4	$111.61	3.566%	$115.59	$115.59	$115.60	$115.60
Purchase #5	$125.90	10.668%	$139.331	$139.33	$139.35	$139.30
Purchase #6	$233.59	7.312%	$250.6701	$250.67	$250.65	$250.70
Purchase #7	$161.31	7.381%	$173.2163	$173.22	$173.20	$173.20
7 purchase totals =	$945.30		$1,025.2176	$1,025.22	$1,025.25	$1,025.20