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	$34.32	5.851%	$36.3281	$36.33	$36.35	$36.30
Purchase #2	$72.72	9.354%	$79.5222	$79.52	$79.50	$79.50
Purchase #3	$88.35	7.434%	$94.9179	$94.92	$94.90	$94.90
Purchase #4	$42.25	7.512%	$45.4238	$45.42	$45.40	$45.40
Purchase #5	$181.38	4.777%	$190.0445	$190.04	$190.05	$190.00
Purchase #6	$101.68	6.331%	$108.1174	$108.12	$108.10	$108.10
Purchase #7	$88.94	13.228%	$100.705	$100.71	$100.70	$100.70
7 purchase totals =	$609.64		$655.0589	$655.06	$655.00	$654.90