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	$118.67	9.795%	$130.2937	$130.29	$130.30	$130.30
Purchase #2	$70.46	4.394%	$73.556	$73.56	$73.55	$73.60
Purchase #3	$56.56	10.813%	$62.6758	$62.68	$62.70	$62.70
Purchase #4	$249.84	9.563%	$273.7322	$273.73	$273.75	$273.70
Purchase #5	$87.85	3.391%	$90.829	$90.83	$90.85	$90.80
Purchase #6	$86.39	13.521%	$98.0708	$98.07	$98.05	$98.10
Purchase #7	$150.36	11.797%	$168.098	$168.10	$168.10	$168.10
7 purchase totals =	$820.13		$897.2555	$897.26	$897.30	$897.30