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	$141.73	6.573%	$151.0459	$151.05	$151.05	$151.00
Purchase #2	$186.83	6.840%	$199.6092	$199.61	$199.60	$199.60
Purchase #3	$150.36	9.457%	$164.5795	$164.58	$164.60	$164.60
Purchase #4	$223.86	8.540%	$242.9776	$242.98	$243.00	$243.00
Purchase #5	$58.32	5.130%	$61.3118	$61.31	$61.30	$61.30
Purchase #6	$8.55	9.683%	$9.3779	$9.38	$9.40	$9.40
Purchase #7	$170.37	8.805%	$185.3711	$185.37	$185.35	$185.40
7 purchase totals =	$940.02		$1,014.2730	$1,014.28	$1,014.30	$1,014.30