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	$90.69	13.663%	$103.081	$103.08	$103.10	$103.10
Purchase #2	$167.64	6.817%	$179.068	$179.07	$179.05	$179.10
Purchase #3	$28.37	6.507%	$30.216	$30.22	$30.20	$30.20
Purchase #4	$144.88	5.669%	$153.0932	$153.09	$153.10	$153.10
Purchase #5	$86.89	13.334%	$98.4759	$98.48	$98.50	$98.50
Purchase #6	$196.84	7.338%	$211.2841	$211.28	$211.30	$211.30
Purchase #7	$31.38	5.769%	$33.1903	$33.19	$33.20	$33.20
7 purchase totals =	$746.69		$808.4085	$808.41	$808.45	$808.50