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	$36.64	5.237%	$38.5588	$38.56	$38.55	$38.60
Purchase #2	$124.29	5.221%	$130.7792	$130.78	$130.80	$130.80
Purchase #3	$168.83	9.745%	$185.2825	$185.28	$185.30	$185.30
Purchase #4	$191.93	10.738%	$212.5394	$212.54	$212.55	$212.50
Purchase #5	$59.32	7.849%	$63.976	$63.98	$64.00	$64.00
Purchase #6	$185.96	10.281%	$205.0785	$205.08	$205.10	$205.10
Purchase #7	$162.72	13.555%	$184.7767	$184.78	$184.80	$184.80
7 purchase totals =	$929.69		$1,020.9911	$1,021.00	$1,021.10	$1,021.10