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	$162.28	10.586%	$179.459	$179.46	$179.45	$179.50
Purchase #2	$240.48	9.629%	$263.6358	$263.64	$263.65	$263.60
Purchase #3	$164.44	9.820%	$180.588	$180.59	$180.60	$180.60
Purchase #4	$110.82	4.429%	$115.7282	$115.73	$115.75	$115.70
Purchase #5	$99.61	4.478%	$104.0705	$104.07	$104.05	$104.10
Purchase #6	$25.25	12.408%	$28.383	$28.38	$28.40	$28.40
Purchase #7	$200.48	6.595%	$213.7017	$213.70	$213.70	$213.70
7 purchase totals =	$1,003.36		$1,085.5662	$1,085.57	$1,085.60	$1,085.60