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	$191.34	10.739%	$211.888	$211.89	$211.90	$211.90
Purchase #2	$179.55	11.629%	$200.4299	$200.43	$200.45	$200.40
Purchase #3	$79.97	13.266%	$90.5788	$90.58	$90.60	$90.60
Purchase #4	$108.32	10.544%	$119.7413	$119.74	$119.75	$119.70
Purchase #5	$161.37	7.822%	$173.9924	$173.99	$174.00	$174.00
Purchase #6	$137.78	13.523%	$156.412	$156.41	$156.40	$156.40
Purchase #7	$134.40	5.147%	$141.3176	$141.32	$141.30	$141.30
7 purchase totals =	$992.73		$1,094.3600	$1,094.36	$1,094.40	$1,094.30