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	$163.87	5.562%	$172.9844	$172.98	$173.00	$173.00
Purchase #2	$56.69	6.639%	$60.4536	$60.45	$60.45	$60.50
Purchase #3	$233.80	12.478%	$262.9736	$262.97	$262.95	$263.00
Purchase #4	$157.41	9.666%	$172.6253	$172.63	$172.65	$172.60
Purchase #5	$50.39	8.727%	$54.7875	$54.79	$54.80	$54.80
Purchase #6	$131.66	7.856%	$142.0032	$142.00	$142.00	$142.00
Purchase #7	$129.90	11.205%	$144.4553	$144.46	$144.45	$144.50
7 purchase totals =	$923.72		$1,010.2829	$1,010.28	$1,010.30	$1,010.40