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	$197.71	11.228%	$219.9089	$219.91	$219.90	$219.90
Purchase #2	$30.27	5.693%	$31.9933	$31.99	$32.00	$32.00
Purchase #3	$94.95	5.867%	$100.5207	$100.52	$100.50	$100.50
Purchase #4	$115.39	10.331%	$127.3109	$127.31	$127.30	$127.30
Purchase #5	$109.31	10.815%	$121.1319	$121.13	$121.15	$121.10
Purchase #6	$54.40	8.677%	$59.1203	$59.12	$59.10	$59.10
Purchase #7	$62.41	5.415%	$65.7895	$65.79	$65.80	$65.80
7 purchase totals =	$664.44		$725.7755	$725.77	$725.75	$725.70