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	$223.66	5.172%	$235.2277	$235.23	$235.25	$235.20
Purchase #2	$42.89	12.716%	$48.3439	$48.34	$48.35	$48.30
Purchase #3	$78.50	8.728%	$85.3515	$85.35	$85.35	$85.40
Purchase #4	$85.69	6.755%	$91.4784	$91.48	$91.50	$91.50
Purchase #5	$244.35	12.362%	$274.5565	$274.56	$274.55	$274.60
Purchase #6	$49.85	12.810%	$56.2358	$56.24	$56.25	$56.20
Purchase #7	$194.39	12.687%	$219.0523	$219.05	$219.05	$219.10
7 purchase totals =	$919.33		$1,010.2461	$1,010.25	$1,010.30	$1,010.30