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	$33.40	10.771%	$36.9975	$37.00	$37.00	$37.00
Purchase #2	$31.45	6.721%	$33.5638	$33.56	$33.55	$33.60
Purchase #3	$33.68	4.801%	$35.297	$35.30	$35.30	$35.30
Purchase #4	$91.91	13.524%	$104.3399	$104.34	$104.35	$104.30
Purchase #5	$51.77	8.469%	$56.1544	$56.15	$56.15	$56.20
Purchase #6	$29.74	13.775%	$33.8367	$33.84	$33.85	$33.80
Purchase #7	$82.53	7.264%	$88.525	$88.53	$88.55	$88.50
7 purchase totals =	$354.48		$388.7143	$388.72	$388.75	$388.70