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	$137.78	4.716%	$144.2777	$144.28	$144.30	$144.30
Purchase #2	$148.90	5.168%	$156.5952	$156.60	$156.60	$156.60
Purchase #3	$200.97	12.693%	$226.4791	$226.48	$226.50	$226.50
Purchase #4	$125.84	12.796%	$141.9425	$141.94	$141.95	$141.90
Purchase #5	$55.77	7.355%	$59.8719	$59.87	$59.85	$59.90
Purchase #6	$115.72	12.608%	$130.31	$130.31	$130.30	$130.30
Purchase #7	$152.25	3.541%	$157.6412	$157.64	$157.65	$157.60
7 purchase totals =	$937.23		$1,017.1176	$1,017.12	$1,017.15	$1,017.10