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	$137.31	4.335%	$143.2624	$143.26	$143.25	$143.30
Purchase #2	$148.52	5.144%	$156.1599	$156.16	$156.15	$156.20
Purchase #3	$30.73	8.627%	$33.3811	$33.38	$33.40	$33.40
Purchase #4	$232.80	3.549%	$241.0621	$241.06	$241.05	$241.10
Purchase #5	$228.76	8.213%	$247.5481	$247.55	$247.55	$247.50
Purchase #6	$136.61	7.136%	$146.3585	$146.36	$146.35	$146.40
Purchase #7	$88.54	3.128%	$91.3095	$91.31	$91.30	$91.30
7 purchase totals =	$1,003.27		$1,059.0816	$1,059.08	$1,059.05	$1,059.20