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	$158.98	9.536%	$174.1403	$174.14	$174.15	$174.10
Purchase #2	$16.43	8.448%	$17.818	$17.82	$17.80	$17.80
Purchase #3	$128.82	3.784%	$133.6945	$133.69	$133.70	$133.70
Purchase #4	$237.42	11.623%	$265.0153	$265.02	$265.00	$265.00
Purchase #5	$131.41	9.833%	$144.3315	$144.33	$144.35	$144.30
Purchase #6	$166.83	4.654%	$174.5943	$174.59	$174.60	$174.60
Purchase #7	$95.30	4.637%	$99.7191	$99.72	$99.70	$99.70
7 purchase totals =	$935.19		$1,009.3130	$1,009.31	$1,009.30	$1,009.20