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	$242.28	3.311%	$250.3019	$250.30	$250.30	$250.30
Purchase #2	$214.59	6.533%	$228.6092	$228.61	$228.60	$228.60
Purchase #3	$179.45	11.395%	$199.8983	$199.90	$199.90	$199.90
Purchase #4	$147.48	3.270%	$152.3026	$152.30	$152.30	$152.30
Purchase #5	$173.86	5.780%	$183.9091	$183.91	$183.90	$183.90
Purchase #6	$35.72	4.459%	$37.3128	$37.31	$37.30	$37.30
Purchase #7	$175.87	13.596%	$199.7813	$199.78	$199.80	$199.80
7 purchase totals =	$1,169.25		$1,252.1152	$1,252.11	$1,252.10	$1,252.10