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	$164.75	4.771%	$172.6102	$172.61	$172.60	$172.60
Purchase #2	$210.80	3.563%	$218.3108	$218.31	$218.30	$218.30
Purchase #3	$18.55	11.782%	$20.7356	$20.74	$20.75	$20.70
Purchase #4	$82.61	5.216%	$86.9189	$86.92	$86.90	$86.90
Purchase #5	$179.79	4.813%	$188.4433	$188.44	$188.45	$188.40
Purchase #6	$184.53	10.663%	$204.2064	$204.21	$204.20	$204.20
Purchase #7	$39.34	7.155%	$42.1548	$42.15	$42.15	$42.20
7 purchase totals =	$880.37		$933.3800	$933.38	$933.35	$933.30