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	$98.61	3.280%	$101.8444	$101.84	$101.85	$101.80
Purchase #2	$247.56	10.409%	$273.3285	$273.33	$273.35	$273.30
Purchase #3	$243.26	11.698%	$271.7166	$271.72	$271.70	$271.70
Purchase #4	$117.81	8.495%	$127.818	$127.82	$127.80	$127.80
Purchase #5	$47.42	11.791%	$53.0113	$53.01	$53.00	$53.00
Purchase #6	$157.39	3.428%	$162.7853	$162.79	$162.80	$162.80
Purchase #7	$76.90	12.831%	$86.767	$86.77	$86.75	$86.80
7 purchase totals =	$988.95		$1,077.2711	$1,077.28	$1,077.25	$1,077.20