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	$103.92	5.593%	$109.7322	$109.73	$109.75	$109.70
Purchase #2	$199.94	5.782%	$211.5005	$211.50	$211.50	$211.50
Purchase #3	$198.56	12.452%	$223.2847	$223.28	$223.30	$223.30
Purchase #4	$73.31	7.492%	$78.8024	$78.80	$78.80	$78.80
Purchase #5	$19.26	7.820%	$20.7661	$20.77	$20.75	$20.80
Purchase #6	$190.39	5.432%	$200.732	$200.73	$200.75	$200.70
Purchase #7	$9.49	7.174%	$10.1708	$10.17	$10.15	$10.20
7 purchase totals =	$794.87		$854.9887	$854.98	$855.00	$855.00