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	$82.87	9.282%	$90.562	$90.56	$90.55	$90.60
Purchase #2	$155.69	5.718%	$164.5924	$164.59	$164.60	$164.60
Purchase #3	$248.61	6.385%	$264.4837	$264.48	$264.50	$264.50
Purchase #4	$157.98	8.515%	$171.432	$171.43	$171.45	$171.40
Purchase #5	$29.87	4.711%	$31.2772	$31.28	$31.30	$31.30
Purchase #6	$107.51	11.787%	$120.1822	$120.18	$120.20	$120.20
Purchase #7	$197.36	12.139%	$221.3175	$221.32	$221.30	$221.30
7 purchase totals =	$979.89		$1,063.8470	$1,063.84	$1,063.90	$1,063.90