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	$178.59	4.442%	$186.523	$186.52	$186.50	$186.50
Purchase #2	$29.43	9.280%	$32.1611	$32.16	$32.15	$32.20
Purchase #3	$183.47	4.687%	$192.0692	$192.07	$192.05	$192.10
Purchase #4	$73.57	11.757%	$82.2196	$82.22	$82.20	$82.20
Purchase #5	$37.84	9.166%	$41.3084	$41.31	$41.30	$41.30
Purchase #6	$83.53	9.119%	$91.1471	$91.15	$91.15	$91.10
Purchase #7	$107.47	4.582%	$112.3943	$112.39	$112.40	$112.40
7 purchase totals =	$693.90		$737.8227	$737.82	$737.75	$737.80