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	$200.42	3.223%	$206.8795	$206.88	$206.90	$206.90
Purchase #2	$27.41	11.353%	$30.5219	$30.52	$30.50	$30.50
Purchase #3	$236.97	11.149%	$263.3898	$263.39	$263.40	$263.40
Purchase #4	$151.41	9.404%	$165.6486	$165.65	$165.65	$165.60
Purchase #5	$90.74	9.633%	$99.481	$99.48	$99.50	$99.50
Purchase #6	$100.33	4.279%	$104.6231	$104.62	$104.60	$104.60
Purchase #7	$156.83	9.514%	$171.7508	$171.75	$171.75	$171.80
7 purchase totals =	$964.11		$1,042.2947	$1,042.29	$1,042.30	$1,042.30