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	$90.65	13.317%	$102.7219	$102.72	$102.70	$102.70
Purchase #2	$79.98	3.225%	$82.5594	$82.56	$82.55	$82.60
Purchase #3	$215.59	3.293%	$222.6894	$222.69	$222.70	$222.70
Purchase #4	$162.83	7.268%	$174.6645	$174.66	$174.65	$174.70
Purchase #5	$181.77	8.272%	$196.806	$196.81	$196.80	$196.80
Purchase #6	$245.49	12.711%	$276.6942	$276.69	$276.70	$276.70
Purchase #7	$36.99	6.723%	$39.4768	$39.48	$39.50	$39.50
7 purchase totals =	$1,013.30		$1,095.6122	$1,095.61	$1,095.60	$1,095.70