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	$148.41	4.387%	$154.9207	$154.92	$154.90	$154.90
Purchase #2	$84.53	6.744%	$90.2307	$90.23	$90.25	$90.20
Purchase #3	$136.29	9.284%	$148.9432	$148.94	$148.95	$148.90
Purchase #4	$241.25	3.863%	$250.5695	$250.57	$250.55	$250.60
Purchase #5	$30.56	3.185%	$31.5333	$31.53	$31.55	$31.50
Purchase #6	$80.57	3.164%	$83.1192	$83.12	$83.10	$83.10
Purchase #7	$87.28	13.450%	$99.0192	$99.02	$99.00	$99.00
7 purchase totals =	$808.89		$858.3358	$858.33	$858.30	$858.20