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	$169.56	3.862%	$176.1084	$176.11	$176.10	$176.10
Purchase #2	$80.67	8.842%	$87.8028	$87.80	$87.80	$87.80
Purchase #3	$246.69	3.269%	$254.7543	$254.75	$254.75	$254.80
Purchase #4	$134.73	3.378%	$139.2812	$139.28	$139.30	$139.30
Purchase #5	$162.46	5.605%	$171.5659	$171.57	$171.55	$171.60
Purchase #6	$104.87	5.860%	$111.0154	$111.02	$111.00	$111.00
Purchase #7	$191.89	9.370%	$209.8701	$209.87	$209.85	$209.90
7 purchase totals =	$1,090.87		$1,150.3981	$1,150.40	$1,150.35	$1,150.50