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	$118.74	10.693%	$131.4369	$131.44	$131.45	$131.40
Purchase #2	$210.55	11.761%	$235.3128	$235.31	$235.30	$235.30
Purchase #3	$63.69	12.788%	$71.8347	$71.83	$71.85	$71.80
Purchase #4	$200.58	10.307%	$221.2538	$221.25	$221.25	$221.30
Purchase #5	$25.30	9.858%	$27.7941	$27.79	$27.80	$27.80
Purchase #6	$57.51	8.769%	$62.5531	$62.55	$62.55	$62.60
Purchase #7	$28.50	11.286%	$31.7165	$31.72	$31.70	$31.70
7 purchase totals =	$704.87		$781.9019	$781.89	$781.90	$781.90