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	$238.41	5.214%	$250.8407	$250.84	$250.85	$250.80
Purchase #2	$59.55	9.185%	$65.0197	$65.02	$65.00	$65.00
Purchase #3	$86.40	5.817%	$91.4259	$91.43	$91.45	$91.40
Purchase #4	$207.86	8.107%	$224.7112	$224.71	$224.70	$224.70
Purchase #5	$147.29	5.809%	$155.8461	$155.85	$155.85	$155.80
Purchase #6	$53.93	10.564%	$59.6272	$59.63	$59.65	$59.60
Purchase #7	$100.82	13.309%	$114.2381	$114.24	$114.25	$114.20
7 purchase totals =	$894.26		$961.7089	$961.72	$961.75	$961.50