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	$232.66	8.767%	$253.0573	$253.06	$253.05	$253.10
Purchase #2	$134.75	8.764%	$146.5595	$146.56	$146.55	$146.60
Purchase #3	$240.97	7.503%	$259.05	$259.05	$259.05	$259.10
Purchase #4	$48.89	12.212%	$54.8604	$54.86	$54.85	$54.90
Purchase #5	$38.34	11.815%	$42.8699	$42.87	$42.85	$42.90
Purchase #6	$17.53	12.354%	$19.6957	$19.70	$19.70	$19.70
Purchase #7	$11.71	7.474%	$12.5852	$12.59	$12.60	$12.60
7 purchase totals =	$724.85		$788.6780	$788.69	$788.65	$788.90