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	$205.54	7.473%	$220.9	$220.90	$220.90	$220.90
Purchase #2	$150.40	10.212%	$165.7588	$165.76	$165.75	$165.80
Purchase #3	$60.28	3.510%	$62.3958	$62.40	$62.40	$62.40
Purchase #4	$115.48	8.470%	$125.2612	$125.26	$125.25	$125.30
Purchase #5	$131.59	3.463%	$136.147	$136.15	$136.15	$136.10
Purchase #6	$94.43	11.665%	$105.4453	$105.45	$105.45	$105.40
Purchase #7	$162.30	9.840%	$178.2703	$178.27	$178.25	$178.30
7 purchase totals =	$920.02		$994.1784	$994.19	$994.15	$994.20