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	$171.46	13.234%	$194.151	$194.15	$194.15	$194.20
Purchase #2	$56.36	3.679%	$58.4335	$58.43	$58.45	$58.40
Purchase #3	$58.42	6.654%	$62.3073	$62.31	$62.30	$62.30
Purchase #4	$135.93	10.656%	$150.4147	$150.41	$150.40	$150.40
Purchase #5	$116.73	3.545%	$120.8681	$120.87	$120.85	$120.90
Purchase #6	$95.49	5.288%	$100.5395	$100.54	$100.55	$100.50
Purchase #7	$39.98	7.570%	$43.0065	$43.01	$43.00	$43.00
7 purchase totals =	$674.37		$729.7206	$729.72	$729.70	$729.70