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	$211.82	3.538%	$219.3142	$219.31	$219.30	$219.30
Purchase #2	$83.72	6.450%	$89.1199	$89.12	$89.10	$89.10
Purchase #3	$207.44	12.649%	$233.6791	$233.68	$233.70	$233.70
Purchase #4	$215.52	5.435%	$227.2335	$227.23	$227.25	$227.20
Purchase #5	$94.31	11.364%	$105.0274	$105.03	$105.05	$105.00
Purchase #6	$221.98	8.718%	$241.3322	$241.33	$241.35	$241.30
Purchase #7	$93.80	9.419%	$102.635	$102.64	$102.65	$102.60
7 purchase totals =	$1,128.59		$1,218.3413	$1,218.34	$1,218.40	$1,218.20