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	$86.36	3.211%	$89.133	$89.13	$89.15	$89.10
Purchase #2	$68.48	7.723%	$73.7687	$73.77	$73.75	$73.80
Purchase #3	$182.79	7.589%	$196.6619	$196.66	$196.65	$196.70
Purchase #4	$240.86	13.116%	$272.4512	$272.45	$272.45	$272.50
Purchase #5	$142.30	3.316%	$147.0187	$147.02	$147.00	$147.00
Purchase #6	$87.93	5.641%	$92.8901	$92.89	$92.90	$92.90
Purchase #7	$129.75	5.461%	$136.8356	$136.84	$136.85	$136.80
7 purchase totals =	$938.47		$1,008.7592	$1,008.76	$1,008.75	$1,008.80