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	$165.30	9.557%	$181.0977	$181.10	$181.10	$181.10
Purchase #2	$200.85	3.349%	$207.5765	$207.58	$207.60	$207.60
Purchase #3	$192.63	4.116%	$200.5587	$200.56	$200.55	$200.60
Purchase #4	$35.65	5.301%	$37.5398	$37.54	$37.55	$37.50
Purchase #5	$169.99	13.148%	$192.3403	$192.34	$192.35	$192.30
Purchase #6	$65.62	8.826%	$71.4116	$71.41	$71.40	$71.40
Purchase #7	$178.27	4.142%	$185.6539	$185.65	$185.65	$185.70
7 purchase totals =	$1,008.31		$1,076.1785	$1,076.18	$1,076.20	$1,076.20