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	$156.33	12.133%	$175.2975	$175.30	$175.30	$175.30
Purchase #2	$233.48	8.296%	$252.8495	$252.85	$252.85	$252.80
Purchase #3	$112.68	13.273%	$127.636	$127.64	$127.65	$127.60
Purchase #4	$53.43	11.274%	$59.4537	$59.45	$59.45	$59.50
Purchase #5	$31.61	9.464%	$34.6016	$34.60	$34.60	$34.60
Purchase #6	$209.76	6.524%	$223.4447	$223.44	$223.45	$223.40
Purchase #7	$18.63	10.651%	$20.6143	$20.61	$20.60	$20.60
7 purchase totals =	$815.92		$893.8973	$893.89	$893.90	$893.80