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	$47.37	11.201%	$52.6759	$52.68	$52.70	$52.70
Purchase #2	$178.66	3.721%	$185.3079	$185.31	$185.30	$185.30
Purchase #3	$45.94	11.844%	$51.3811	$51.38	$51.40	$51.40
Purchase #4	$182.74	6.389%	$194.4153	$194.42	$194.40	$194.40
Purchase #5	$82.88	8.660%	$90.0574	$90.06	$90.05	$90.10
Purchase #6	$158.39	12.552%	$178.2711	$178.27	$178.25	$178.30
Purchase #7	$38.89	4.299%	$40.5619	$40.56	$40.55	$40.60
7 purchase totals =	$734.87		$792.6706	$792.68	$792.65	$792.80