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	$162.89	3.181%	$168.0715	$168.07	$168.05	$168.10
Purchase #2	$173.36	11.236%	$192.8387	$192.84	$192.85	$192.80
Purchase #3	$52.44	4.822%	$54.9687	$54.97	$54.95	$55.00
Purchase #4	$108.65	10.514%	$120.0735	$120.07	$120.05	$120.10
Purchase #5	$61.93	3.547%	$64.1267	$64.13	$64.15	$64.10
Purchase #6	$217.33	11.144%	$241.5493	$241.55	$241.55	$241.50
Purchase #7	$88.88	11.711%	$99.2887	$99.29	$99.30	$99.30
7 purchase totals =	$865.48		$940.9171	$940.92	$940.90	$940.90