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	$165.36	13.377%	$187.4802	$187.48	$187.50	$187.50
Purchase #2	$179.80	6.764%	$191.9617	$191.96	$191.95	$192.00
Purchase #3	$128.50	6.654%	$137.0504	$137.05	$137.05	$137.10
Purchase #4	$234.95	12.384%	$264.0462	$264.05	$264.05	$264.00
Purchase #5	$31.35	3.347%	$32.3993	$32.40	$32.40	$32.40
Purchase #6	$129.86	9.601%	$142.3279	$142.33	$142.35	$142.30
Purchase #7	$192.73	10.835%	$213.6123	$213.61	$213.60	$213.60
7 purchase totals =	$1,062.55		$1,168.8780	$1,168.88	$1,168.90	$1,168.90