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	$170.90	9.462%	$187.0706	$187.07	$187.05	$187.10
Purchase #2	$61.97	3.826%	$64.341	$64.34	$64.35	$64.30
Purchase #3	$98.97	8.551%	$107.4329	$107.43	$107.45	$107.40
Purchase #4	$57.41	3.590%	$59.471	$59.47	$59.45	$59.50
Purchase #5	$249.32	6.590%	$265.7502	$265.75	$265.75	$265.80
Purchase #6	$205.64	11.604%	$229.5025	$229.50	$229.50	$229.50
Purchase #7	$127.89	9.326%	$139.817	$139.82	$139.80	$139.80
7 purchase totals =	$972.10		$1,053.3852	$1,053.38	$1,053.35	$1,053.40