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	$215.32	10.638%	$238.2257	$238.23	$238.25	$238.20
Purchase #2	$12.82	11.671%	$14.3162	$14.32	$14.30	$14.30
Purchase #3	$209.39	6.858%	$223.75	$223.75	$223.75	$223.80
Purchase #4	$76.89	10.773%	$85.1734	$85.17	$85.15	$85.20
Purchase #5	$56.61	9.122%	$61.774	$61.77	$61.75	$61.80
Purchase #6	$126.68	8.133%	$136.9829	$136.98	$137.00	$137.00
Purchase #7	$165.84	7.658%	$178.54	$178.54	$178.55	$178.50
7 purchase totals =	$863.55		$938.7622	$938.76	$938.75	$938.80