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	$151.44	13.593%	$172.0252	$172.03	$172.05	$172.00
Purchase #2	$94.64	4.131%	$98.5496	$98.55	$98.55	$98.50
Purchase #3	$110.33	7.858%	$118.9997	$119.00	$119.00	$119.00
Purchase #4	$214.97	4.463%	$224.5641	$224.56	$224.55	$224.60
Purchase #5	$38.69	9.563%	$42.3899	$42.39	$42.40	$42.40
Purchase #6	$145.63	11.860%	$162.9017	$162.90	$162.90	$162.90
Purchase #7	$165.53	5.795%	$175.1225	$175.12	$175.10	$175.10
7 purchase totals =	$921.23		$994.5527	$994.55	$994.55	$994.50