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	$40.65	7.172%	$43.5654	$43.57	$43.55	$43.60
Purchase #2	$35.37	9.171%	$38.6138	$38.61	$38.60	$38.60
Purchase #3	$228.31	6.766%	$243.7575	$243.76	$243.75	$243.80
Purchase #4	$90.27	7.258%	$96.8218	$96.82	$96.80	$96.80
Purchase #5	$42.59	4.355%	$44.4448	$44.44	$44.45	$44.40
Purchase #6	$160.30	4.314%	$167.2153	$167.22	$167.20	$167.20
Purchase #7	$105.27	6.223%	$111.821	$111.82	$111.80	$111.80
7 purchase totals =	$702.76		$746.2396	$746.24	$746.15	$746.20