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	$205.37	11.673%	$229.3428	$229.34	$229.35	$229.30
Purchase #2	$118.85	4.219%	$123.8643	$123.86	$123.85	$123.90
Purchase #3	$128.77	3.604%	$133.4109	$133.41	$133.40	$133.40
Purchase #4	$195.46	8.345%	$211.7711	$211.77	$211.75	$211.80
Purchase #5	$142.97	5.654%	$151.0535	$151.05	$151.05	$151.10
Purchase #6	$215.42	10.356%	$237.7289	$237.73	$237.75	$237.70
Purchase #7	$54.48	13.479%	$61.8234	$61.82	$61.80	$61.80
7 purchase totals =	$1,061.32		$1,148.9949	$1,148.98	$1,148.95	$1,149.00