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	$114.66	7.486%	$123.2434	$123.24	$123.25	$123.20
Purchase #2	$168.54	5.799%	$178.3136	$178.31	$178.30	$178.30
Purchase #3	$113.61	9.596%	$124.512	$124.51	$124.50	$124.50
Purchase #4	$243.88	6.683%	$260.1785	$260.18	$260.20	$260.20
Purchase #5	$219.61	10.681%	$243.0665	$243.07	$243.05	$243.10
Purchase #6	$64.46	9.300%	$70.4548	$70.45	$70.45	$70.50
Purchase #7	$129.76	7.421%	$139.3895	$139.39	$139.40	$139.40
7 purchase totals =	$1,054.52		$1,139.1583	$1,139.15	$1,139.15	$1,139.20