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	$69.67	3.237%	$71.9252	$71.93	$71.95	$71.90
Purchase #2	$66.95	7.270%	$71.8173	$71.82	$71.80	$71.80
Purchase #3	$100.68	4.500%	$105.2106	$105.21	$105.20	$105.20
Purchase #4	$98.35	13.107%	$111.2407	$111.24	$111.25	$111.20
Purchase #5	$219.92	5.644%	$232.3323	$232.33	$232.35	$232.30
Purchase #6	$150.85	11.234%	$167.7965	$167.80	$167.80	$167.80
Purchase #7	$21.51	13.477%	$24.4089	$24.41	$24.40	$24.40
7 purchase totals =	$727.93		$784.7315	$784.74	$784.75	$784.60