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	$197.69	12.347%	$222.0988	$222.10	$222.10	$222.10
Purchase #2	$187.89	4.473%	$196.2943	$196.29	$196.30	$196.30
Purchase #3	$13.97	6.727%	$14.9098	$14.91	$14.90	$14.90
Purchase #4	$51.65	6.441%	$54.9768	$54.98	$55.00	$55.00
Purchase #5	$71.74	11.568%	$80.0389	$80.04	$80.05	$80.00
Purchase #6	$104.83	7.153%	$112.3285	$112.33	$112.35	$112.30
Purchase #7	$153.75	10.679%	$170.169	$170.17	$170.15	$170.20
7 purchase totals =	$781.52		$850.8161	$850.82	$850.85	$850.80