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	$164.28	9.152%	$179.3149	$179.31	$179.30	$179.30
Purchase #2	$57.32	12.637%	$64.5635	$64.56	$64.55	$64.60
Purchase #3	$228.99	3.568%	$237.1604	$237.16	$237.15	$237.20
Purchase #4	$35.50	13.578%	$40.3202	$40.32	$40.30	$40.30
Purchase #5	$248.53	6.591%	$264.9106	$264.91	$264.90	$264.90
Purchase #6	$143.39	13.168%	$162.2716	$162.27	$162.25	$162.30
Purchase #7	$205.61	9.847%	$225.8564	$225.86	$225.85	$225.90
7 purchase totals =	$1,083.62		$1,174.3976	$1,174.39	$1,174.30	$1,174.50