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	$203.64	9.692%	$223.3768	$223.38	$223.40	$223.40
Purchase #2	$150.80	12.764%	$170.0481	$170.05	$170.05	$170.00
Purchase #3	$29.31	9.272%	$32.0276	$32.03	$32.05	$32.00
Purchase #4	$229.90	10.232%	$253.4234	$253.42	$253.40	$253.40
Purchase #5	$156.89	12.376%	$176.3067	$176.31	$176.30	$176.30
Purchase #6	$78.87	8.429%	$85.518	$85.52	$85.50	$85.50
Purchase #7	$162.47	7.449%	$174.5724	$174.57	$174.55	$174.60
7 purchase totals =	$1,011.88		$1,115.2730	$1,115.28	$1,115.25	$1,115.20