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	$91.27	13.543%	$103.6307	$103.63	$103.65	$103.60
Purchase #2	$112.38	10.835%	$124.5564	$124.56	$124.55	$124.60
Purchase #3	$86.73	5.195%	$91.2356	$91.24	$91.25	$91.20
Purchase #4	$211.93	5.780%	$224.1796	$224.18	$224.20	$224.20
Purchase #5	$81.49	4.578%	$85.2206	$85.22	$85.20	$85.20
Purchase #6	$226.54	3.216%	$233.8255	$233.83	$233.85	$233.80
Purchase #7	$211.42	8.389%	$229.156	$229.16	$229.15	$229.20
7 purchase totals =	$1,021.76		$1,091.8044	$1,091.82	$1,091.85	$1,091.80