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	$245.54	7.284%	$263.4251	$263.43	$263.45	$263.40
Purchase #2	$109.65	6.536%	$116.8167	$116.82	$116.80	$116.80
Purchase #3	$30.45	5.274%	$32.0559	$32.06	$32.05	$32.10
Purchase #4	$53.76	3.653%	$55.7239	$55.72	$55.70	$55.70
Purchase #5	$245.30	7.640%	$264.0409	$264.04	$264.05	$264.00
Purchase #6	$227.34	7.546%	$244.4951	$244.50	$244.50	$244.50
Purchase #7	$86.90	4.436%	$90.7549	$90.75	$90.75	$90.80
7 purchase totals =	$998.94		$1,067.3125	$1,067.32	$1,067.30	$1,067.30