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	$177.78	3.551%	$184.093	$184.09	$184.10	$184.10
Purchase #2	$189.28	3.722%	$196.325	$196.33	$196.35	$196.30
Purchase #3	$156.47	8.728%	$170.1267	$170.13	$170.15	$170.10
Purchase #4	$202.26	10.729%	$223.9605	$223.96	$223.95	$224.00
Purchase #5	$79.26	5.201%	$83.3823	$83.38	$83.40	$83.40
Purchase #6	$82.61	13.463%	$93.7318	$93.73	$93.75	$93.70
Purchase #7	$40.41	6.204%	$42.917	$42.92	$42.90	$42.90
7 purchase totals =	$928.07		$994.5363	$994.54	$994.60	$994.50