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	$210.31	4.475%	$219.7214	$219.72	$219.70	$219.70
Purchase #2	$36.70	12.343%	$41.2299	$41.23	$41.25	$41.20
Purchase #3	$81.82	9.294%	$89.4244	$89.42	$89.40	$89.40
Purchase #4	$159.84	9.185%	$174.5213	$174.52	$174.50	$174.50
Purchase #5	$233.60	5.861%	$247.2913	$247.29	$247.30	$247.30
Purchase #6	$41.61	10.355%	$45.9187	$45.92	$45.90	$45.90
Purchase #7	$202.60	4.254%	$211.2186	$211.22	$211.20	$211.20
7 purchase totals =	$966.48		$1,029.3256	$1,029.32	$1,029.25	$1,029.20