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	$40.51	7.158%	$43.4097	$43.41	$43.40	$43.40
Purchase #2	$19.42	4.246%	$20.2446	$20.24	$20.25	$20.20
Purchase #3	$104.93	8.662%	$114.019	$114.02	$114.00	$114.00
Purchase #4	$48.85	9.634%	$53.5562	$53.56	$53.55	$53.60
Purchase #5	$209.87	6.559%	$223.6354	$223.64	$223.65	$223.60
Purchase #6	$105.88	3.587%	$109.6779	$109.68	$109.70	$109.70
Purchase #7	$96.32	11.411%	$107.3111	$107.31	$107.30	$107.30
7 purchase totals =	$625.78		$671.8539	$671.86	$671.85	$671.80