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	$130.78	11.110%	$145.3097	$145.31	$145.30	$145.30
Purchase #2	$99.92	3.776%	$103.693	$103.69	$103.70	$103.70
Purchase #3	$78.80	11.360%	$87.7517	$87.75	$87.75	$87.80
Purchase #4	$84.75	12.352%	$95.2183	$95.22	$95.20	$95.20
Purchase #5	$72.84	7.497%	$78.3008	$78.30	$78.30	$78.30
Purchase #6	$139.93	11.736%	$156.3522	$156.35	$156.35	$156.40
Purchase #7	$225.75	9.736%	$247.729	$247.73	$247.75	$247.70
7 purchase totals =	$832.77		$914.3547	$914.35	$914.35	$914.40