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	$233.33	6.777%	$249.1428	$249.14	$249.15	$249.10
Purchase #2	$63.97	12.729%	$72.1127	$72.11	$72.10	$72.10
Purchase #3	$105.97	13.318%	$120.0831	$120.08	$120.10	$120.10
Purchase #4	$35.36	5.430%	$37.28	$37.28	$37.30	$37.30
Purchase #5	$128.29	13.864%	$146.0761	$146.08	$146.10	$146.10
Purchase #6	$185.98	4.805%	$194.9163	$194.92	$194.90	$194.90
Purchase #7	$181.88	5.483%	$191.8525	$191.85	$191.85	$191.90
7 purchase totals =	$934.78		$1,011.4635	$1,011.46	$1,011.50	$1,011.50