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	$72.97	7.321%	$78.3121	$78.31	$78.30	$78.30
Purchase #2	$148.41	3.736%	$153.9546	$153.95	$153.95	$154.00
Purchase #3	$148.94	9.335%	$162.8435	$162.84	$162.85	$162.80
Purchase #4	$118.41	9.874%	$130.1018	$130.10	$130.10	$130.10
Purchase #5	$55.32	7.289%	$59.3523	$59.35	$59.35	$59.40
Purchase #6	$197.45	10.236%	$217.661	$217.66	$217.65	$217.70
Purchase #7	$190.48	11.749%	$212.8595	$212.86	$212.85	$212.90
7 purchase totals =	$931.98		$1,015.0848	$1,015.07	$1,015.05	$1,015.20