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	$150.49	13.457%	$170.7414	$170.74	$170.75	$170.70
Purchase #2	$118.47	7.484%	$127.3363	$127.34	$127.35	$127.30
Purchase #3	$98.59	6.436%	$104.9353	$104.94	$104.95	$104.90
Purchase #4	$41.60	10.471%	$45.9559	$45.96	$45.95	$46.00
Purchase #5	$200.32	6.603%	$213.5471	$213.55	$213.55	$213.50
Purchase #6	$209.72	6.440%	$223.226	$223.23	$223.25	$223.20
Purchase #7	$232.98	13.260%	$263.8731	$263.87	$263.85	$263.90
7 purchase totals =	$1,052.17		$1,149.6151	$1,149.63	$1,149.65	$1,149.50