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	$49.25	7.130%	$52.7615	$52.76	$52.75	$52.80
Purchase #2	$232.74	4.432%	$243.055	$243.06	$243.05	$243.10
Purchase #3	$53.87	9.788%	$59.1428	$59.14	$59.15	$59.10
Purchase #4	$126.46	10.790%	$140.105	$140.11	$140.10	$140.10
Purchase #5	$192.94	6.411%	$205.3094	$205.31	$205.30	$205.30
Purchase #6	$177.40	8.106%	$191.78	$191.78	$191.80	$191.80
Purchase #7	$170.63	7.195%	$182.9068	$182.91	$182.90	$182.90
7 purchase totals =	$1,003.29		$1,075.0605	$1,075.07	$1,075.05	$1,075.10