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	$94.75	4.754%	$99.2544	$99.25	$99.25	$99.30
Purchase #2	$227.90	7.299%	$244.5344	$244.53	$244.55	$244.50
Purchase #3	$82.91	8.685%	$90.1107	$90.11	$90.10	$90.10
Purchase #4	$114.83	4.426%	$119.9124	$119.91	$119.90	$119.90
Purchase #5	$205.38	8.514%	$222.8661	$222.87	$222.85	$222.90
Purchase #6	$116.52	12.700%	$131.318	$131.32	$131.30	$131.30
Purchase #7	$249.41	7.623%	$268.4225	$268.42	$268.40	$268.40
7 purchase totals =	$1,091.70		$1,176.4185	$1,176.41	$1,176.35	$1,176.40