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	$47.85	10.575%	$52.9101	$52.91	$52.90	$52.90
Purchase #2	$165.85	9.830%	$182.1531	$182.15	$182.15	$182.20
Purchase #3	$189.60	12.288%	$212.898	$212.90	$212.90	$212.90
Purchase #4	$144.44	11.159%	$160.5581	$160.56	$160.55	$160.60
Purchase #5	$230.35	4.524%	$240.771	$240.77	$240.75	$240.80
Purchase #6	$48.92	7.282%	$52.4824	$52.48	$52.50	$52.50
Purchase #7	$97.85	8.214%	$105.8874	$105.89	$105.90	$105.90
7 purchase totals =	$924.86		$1,007.6601	$1,007.66	$1,007.65	$1,007.80