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	$162.75	6.765%	$173.76	$173.76	$173.75	$173.80
Purchase #2	$78.25	5.278%	$82.38	$82.38	$82.40	$82.40
Purchase #3	$162.69	6.652%	$173.5121	$173.51	$173.50	$173.50
Purchase #4	$238.79	13.241%	$270.4082	$270.41	$270.40	$270.40
Purchase #5	$234.67	4.373%	$244.9321	$244.93	$244.95	$244.90
Purchase #6	$234.77	3.710%	$243.48	$243.48	$243.50	$243.50
Purchase #7	$107.31	6.614%	$114.4075	$114.41	$114.40	$114.40
7 purchase totals =	$1,219.23		$1,302.8799	$1,302.88	$1,302.90	$1,302.90