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	$39.44	7.489%	$42.3937	$42.39	$42.40	$42.40
Purchase #2	$90.43	8.171%	$97.819	$97.82	$97.80	$97.80
Purchase #3	$82.65	10.195%	$91.0762	$91.08	$91.10	$91.10
Purchase #4	$157.71	10.690%	$174.5692	$174.57	$174.55	$174.60
Purchase #5	$175.59	6.518%	$187.035	$187.04	$187.05	$187.00
Purchase #6	$76.56	3.151%	$78.9724	$78.97	$78.95	$79.00
Purchase #7	$33.28	7.487%	$35.7717	$35.77	$35.75	$35.80
7 purchase totals =	$655.66		$707.6372	$707.64	$707.60	$707.70