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	$86.69	3.849%	$90.0267	$90.03	$90.05	$90.00
Purchase #2	$147.32	3.841%	$152.9786	$152.98	$153.00	$153.00
Purchase #3	$120.97	5.759%	$127.9367	$127.94	$127.95	$127.90
Purchase #4	$238.25	13.466%	$270.3327	$270.33	$270.35	$270.30
Purchase #5	$159.75	13.458%	$181.2492	$181.25	$181.25	$181.20
Purchase #6	$165.97	4.636%	$173.6644	$173.66	$173.65	$173.70
Purchase #7	$69.45	11.266%	$77.2742	$77.27	$77.25	$77.30
7 purchase totals =	$988.40		$1,073.4625	$1,073.46	$1,073.50	$1,073.40