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	$223.46	4.838%	$234.271	$234.27	$234.25	$234.30
Purchase #2	$198.32	5.560%	$209.3466	$209.35	$209.35	$209.30
Purchase #3	$138.27	13.320%	$156.6876	$156.69	$156.70	$156.70
Purchase #4	$78.73	4.799%	$82.5083	$82.51	$82.50	$82.50
Purchase #5	$237.59	3.467%	$245.8272	$245.83	$245.85	$245.80
Purchase #6	$80.84	11.217%	$89.9078	$89.91	$89.90	$89.90
Purchase #7	$26.83	8.617%	$29.1419	$29.14	$29.15	$29.10
7 purchase totals =	$984.04		$1,047.6904	$1,047.70	$1,047.70	$1,047.60