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	$127.33	11.662%	$142.1792	$142.18	$142.20	$142.20
Purchase #2	$6.98	6.818%	$7.4559	$7.46	$7.45	$7.50
Purchase #3	$76.80	7.867%	$82.8419	$82.84	$82.85	$82.80
Purchase #4	$18.77	4.779%	$19.667	$19.67	$19.65	$19.70
Purchase #5	$26.37	3.401%	$27.2668	$27.27	$27.25	$27.30
Purchase #6	$243.74	8.760%	$265.0916	$265.09	$265.10	$265.10
Purchase #7	$143.90	3.271%	$148.607	$148.61	$148.60	$148.60
7 purchase totals =	$643.89		$693.1094	$693.12	$693.10	$693.20