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	$135.63	4.851%	$142.2094	$142.21	$142.20	$142.20
Purchase #2	$40.63	7.260%	$43.5797	$43.58	$43.60	$43.60
Purchase #3	$206.35	11.435%	$229.9461	$229.95	$229.95	$229.90
Purchase #4	$249.73	6.694%	$266.4469	$266.45	$266.45	$266.40
Purchase #5	$146.83	3.713%	$152.2818	$152.28	$152.30	$152.30
Purchase #6	$16.90	12.564%	$19.0233	$19.02	$19.00	$19.00
Purchase #7	$240.82	12.156%	$270.0941	$270.09	$270.10	$270.10
7 purchase totals =	$1,036.89		$1,123.5813	$1,123.58	$1,123.60	$1,123.50