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	$34.68	4.320%	$36.1782	$36.18	$36.20	$36.20
Purchase #2	$194.32	11.460%	$216.5891	$216.59	$216.60	$216.60
Purchase #3	$50.60	7.399%	$54.3439	$54.34	$54.35	$54.30
Purchase #4	$90.56	9.154%	$98.8499	$98.85	$98.85	$98.80
Purchase #5	$159.62	5.179%	$167.8867	$167.89	$167.90	$167.90
Purchase #6	$76.61	4.275%	$79.8851	$79.89	$79.90	$79.90
Purchase #7	$223.53	13.199%	$253.0337	$253.03	$253.05	$253.00
7 purchase totals =	$829.92		$906.7666	$906.77	$906.85	$906.70