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	$29.92	9.257%	$32.6897	$32.69	$32.70	$32.70
Purchase #2	$80.46	13.398%	$91.24	$91.24	$91.25	$91.20
Purchase #3	$107.78	3.725%	$111.7948	$111.79	$111.80	$111.80
Purchase #4	$150.72	7.552%	$162.1024	$162.10	$162.10	$162.10
Purchase #5	$181.44	8.402%	$196.6846	$196.68	$196.70	$196.70
Purchase #6	$193.30	4.527%	$202.0507	$202.05	$202.05	$202.10
Purchase #7	$245.93	9.589%	$269.5122	$269.51	$269.50	$269.50
7 purchase totals =	$989.55		$1,066.0744	$1,066.06	$1,066.10	$1,066.10