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	$143.90	4.553%	$150.4518	$150.45	$150.45	$150.50
Purchase #2	$204.63	5.211%	$215.2933	$215.29	$215.30	$215.30
Purchase #3	$90.44	8.674%	$98.2848	$98.28	$98.30	$98.30
Purchase #4	$167.79	8.572%	$182.173	$182.17	$182.15	$182.20
Purchase #5	$8.69	8.302%	$9.4114	$9.41	$9.40	$9.40
Purchase #6	$248.48	3.403%	$256.9358	$256.94	$256.95	$256.90
Purchase #7	$80.60	12.222%	$90.4509	$90.45	$90.45	$90.50
7 purchase totals =	$944.53		$1,003.0010	$1,002.99	$1,003.00	$1,003.10