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	$79.73	7.325%	$85.5702	$85.57	$85.55	$85.60
Purchase #2	$54.97	10.163%	$60.5566	$60.56	$60.55	$60.60
Purchase #3	$192.63	10.250%	$212.3746	$212.37	$212.35	$212.40
Purchase #4	$46.51	3.751%	$48.2546	$48.25	$48.25	$48.30
Purchase #5	$92.78	11.756%	$103.6872	$103.69	$103.70	$103.70
Purchase #6	$42.36	12.263%	$47.5546	$47.55	$47.55	$47.60
Purchase #7	$31.83	10.432%	$35.1505	$35.15	$35.15	$35.20
7 purchase totals =	$540.81		$593.1483	$593.14	$593.10	$593.40