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	$134.98	5.621%	$142.5672	$142.57	$142.55	$142.60
Purchase #2	$243.40	6.459%	$259.1212	$259.12	$259.10	$259.10
Purchase #3	$52.34	13.315%	$59.3091	$59.31	$59.30	$59.30
Purchase #4	$165.84	10.310%	$182.9381	$182.94	$182.95	$182.90
Purchase #5	$248.89	5.607%	$262.8453	$262.85	$262.85	$262.80
Purchase #6	$65.31	6.356%	$69.4611	$69.46	$69.45	$69.50
Purchase #7	$42.43	3.111%	$43.75	$43.75	$43.75	$43.80
7 purchase totals =	$953.19		$1,019.9920	$1,020.00	$1,019.95	$1,020.00