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	$140.51	3.710%	$145.7229	$145.72	$145.70	$145.70
Purchase #2	$244.72	9.673%	$268.3918	$268.39	$268.40	$268.40
Purchase #3	$145.26	10.813%	$160.967	$160.97	$160.95	$161.00
Purchase #4	$225.45	3.555%	$233.4647	$233.46	$233.45	$233.50
Purchase #5	$221.56	5.495%	$233.7347	$233.73	$233.75	$233.70
Purchase #6	$55.36	4.431%	$57.813	$57.81	$57.80	$57.80
Purchase #7	$82.88	9.650%	$90.8779	$90.88	$90.90	$90.90
7 purchase totals =	$1,115.74		$1,190.9720	$1,190.96	$1,190.95	$1,191.00