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	$125.74	11.412%	$140.0894	$140.09	$140.10	$140.10
Purchase #2	$68.88	5.728%	$72.8254	$72.83	$72.85	$72.80
Purchase #3	$240.34	4.208%	$250.4535	$250.45	$250.45	$250.50
Purchase #4	$144.79	8.199%	$156.6613	$156.66	$156.65	$156.70
Purchase #5	$186.33	6.487%	$198.4172	$198.42	$198.40	$198.40
Purchase #6	$88.57	4.550%	$92.5999	$92.60	$92.60	$92.60
Purchase #7	$168.52	12.572%	$189.7063	$189.71	$189.70	$189.70
7 purchase totals =	$1,023.17		$1,100.7530	$1,100.76	$1,100.75	$1,100.80