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	$161.75	10.675%	$179.0168	$179.02	$179.00	$179.00
Purchase #2	$143.35	11.234%	$159.4539	$159.45	$159.45	$159.50
Purchase #3	$99.76	5.254%	$105.0014	$105.00	$105.00	$105.00
Purchase #4	$37.46	6.562%	$39.9181	$39.92	$39.90	$39.90
Purchase #5	$94.61	10.241%	$104.299	$104.30	$104.30	$104.30
Purchase #6	$178.70	11.524%	$199.2934	$199.29	$199.30	$199.30
Purchase #7	$20.29	5.190%	$21.3431	$21.34	$21.35	$21.30
7 purchase totals =	$735.92		$808.3257	$808.32	$808.30	$808.30