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	$184.25	6.670%	$196.5395	$196.54	$196.55	$196.50
Purchase #2	$134.56	11.694%	$150.2954	$150.30	$150.30	$150.30
Purchase #3	$242.88	10.711%	$268.8949	$268.89	$268.90	$268.90
Purchase #4	$100.58	12.319%	$112.9705	$112.97	$112.95	$113.00
Purchase #5	$193.41	8.158%	$209.1884	$209.19	$209.20	$209.20
Purchase #6	$245.72	8.231%	$265.9452	$265.95	$265.95	$265.90
Purchase #7	$62.87	3.861%	$65.2974	$65.30	$65.30	$65.30
7 purchase totals =	$1,164.27		$1,269.1313	$1,269.14	$1,269.15	$1,269.10