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	$87.91	9.245%	$96.0373	$96.04	$96.05	$96.00
Purchase #2	$188.44	12.800%	$212.5603	$212.56	$212.55	$212.60
Purchase #3	$227.84	12.390%	$256.0694	$256.07	$256.05	$256.10
Purchase #4	$149.31	10.118%	$164.4172	$164.42	$164.40	$164.40
Purchase #5	$181.31	10.343%	$200.0629	$200.06	$200.05	$200.10
Purchase #6	$181.50	10.368%	$200.3179	$200.32	$200.30	$200.30
Purchase #7	$17.48	7.142%	$18.7284	$18.73	$18.75	$18.70
7 purchase totals =	$1,033.79		$1,148.1934	$1,148.20	$1,148.15	$1,148.20