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	$147.31	13.343%	$166.9656	$166.97	$166.95	$167.00
Purchase #2	$219.82	10.839%	$243.6463	$243.65	$243.65	$243.60
Purchase #3	$195.31	13.604%	$221.88	$221.88	$221.90	$221.90
Purchase #4	$200.46	10.288%	$221.0833	$221.08	$221.10	$221.10
Purchase #5	$250.85	4.596%	$262.3791	$262.38	$262.40	$262.40
Purchase #6	$85.50	6.783%	$91.2995	$91.30	$91.30	$91.30
Purchase #7	$90.49	4.325%	$94.4037	$94.40	$94.40	$94.40
7 purchase totals =	$1,189.74		$1,301.6575	$1,301.66	$1,301.70	$1,301.70