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	$113.59	12.237%	$127.49	$127.49	$127.50	$127.50
Purchase #2	$41.25	4.212%	$42.9875	$42.99	$43.00	$43.00
Purchase #3	$211.25	4.608%	$220.9844	$220.98	$221.00	$221.00
Purchase #4	$62.44	4.614%	$65.321	$65.32	$65.30	$65.30
Purchase #5	$191.50	4.575%	$200.2611	$200.26	$200.25	$200.30
Purchase #6	$168.52	4.242%	$175.6686	$175.67	$175.65	$175.70
Purchase #7	$156.92	8.403%	$170.106	$170.11	$170.10	$170.10
7 purchase totals =	$945.47		$1,002.8186	$1,002.82	$1,002.80	$1,002.90