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	$21.32	12.814%	$24.0519	$24.05	$24.05	$24.10
Purchase #2	$28.31	8.130%	$30.6116	$30.61	$30.60	$30.60
Purchase #3	$53.34	4.791%	$55.8955	$55.90	$55.90	$55.90
Purchase #4	$144.91	4.132%	$150.8977	$150.90	$150.90	$150.90
Purchase #5	$174.55	5.362%	$183.9094	$183.91	$183.90	$183.90
Purchase #6	$73.26	13.152%	$82.8952	$82.90	$82.90	$82.90
Purchase #7	$182.38	12.581%	$205.3252	$205.33	$205.35	$205.30
7 purchase totals =	$678.07		$733.5865	$733.60	$733.60	$733.60