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	$95.27	9.458%	$104.2806	$104.28	$104.30	$104.30
Purchase #2	$250.54	6.654%	$267.2109	$267.21	$267.20	$267.20
Purchase #3	$88.56	11.652%	$98.879	$98.88	$98.90	$98.90
Purchase #4	$169.78	8.319%	$183.904	$183.90	$183.90	$183.90
Purchase #5	$229.45	9.130%	$250.3988	$250.40	$250.40	$250.40
Purchase #6	$57.57	3.746%	$59.7266	$59.73	$59.75	$59.70
Purchase #7	$97.98	11.802%	$109.5436	$109.54	$109.55	$109.50
7 purchase totals =	$989.15		$1,073.9435	$1,073.94	$1,074.00	$1,073.90