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	$219.98	4.181%	$229.1774	$229.18	$229.20	$229.20
Purchase #2	$62.77	3.824%	$65.1703	$65.17	$65.15	$65.20
Purchase #3	$221.29	3.490%	$229.013	$229.01	$229.00	$229.00
Purchase #4	$30.28	11.150%	$33.6562	$33.66	$33.65	$33.70
Purchase #5	$90.88	11.280%	$101.1313	$101.13	$101.15	$101.10
Purchase #6	$96.99	12.525%	$109.138	$109.14	$109.15	$109.10
Purchase #7	$218.41	5.124%	$229.6013	$229.60	$229.60	$229.60
7 purchase totals =	$940.60		$996.8875	$996.89	$996.90	$996.90