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	$194.40	9.850%	$213.5484	$213.55	$213.55	$213.50
Purchase #2	$153.90	12.227%	$172.7174	$172.72	$172.70	$172.70
Purchase #3	$205.80	8.427%	$223.1428	$223.14	$223.15	$223.10
Purchase #4	$135.77	12.279%	$152.4412	$152.44	$152.45	$152.40
Purchase #5	$79.41	4.565%	$83.0351	$83.04	$83.05	$83.00
Purchase #6	$81.59	5.746%	$86.2782	$86.28	$86.30	$86.30
Purchase #7	$245.73	7.233%	$263.5037	$263.50	$263.50	$263.50
7 purchase totals =	$1,096.60		$1,194.6668	$1,194.67	$1,194.70	$1,194.50