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	$162.96	13.376%	$184.7575	$184.76	$184.75	$184.80
Purchase #2	$83.40	10.709%	$92.3313	$92.33	$92.35	$92.30
Purchase #3	$64.30	12.317%	$72.2198	$72.22	$72.20	$72.20
Purchase #4	$58.65	8.268%	$63.4992	$63.50	$63.50	$63.50
Purchase #5	$91.38	9.502%	$100.0629	$100.06	$100.05	$100.10
Purchase #6	$125.39	4.780%	$131.3836	$131.38	$131.40	$131.40
Purchase #7	$183.89	6.581%	$195.9918	$195.99	$196.00	$196.00
7 purchase totals =	$769.97		$840.2461	$840.24	$840.25	$840.30