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	$223.30	4.592%	$233.5539	$233.55	$233.55	$233.60
Purchase #2	$219.59	7.265%	$235.5432	$235.54	$235.55	$235.50
Purchase #3	$167.72	6.294%	$178.2763	$178.28	$178.30	$178.30
Purchase #4	$155.57	11.474%	$173.4201	$173.42	$173.40	$173.40
Purchase #5	$223.36	6.727%	$238.3854	$238.39	$238.40	$238.40
Purchase #6	$138.68	8.687%	$150.7271	$150.73	$150.75	$150.70
Purchase #7	$92.57	13.304%	$104.8855	$104.89	$104.90	$104.90
7 purchase totals =	$1,220.79		$1,314.7915	$1,314.80	$1,314.85	$1,314.80