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	$195.88	6.858%	$209.3135	$209.31	$209.30	$209.30
Purchase #2	$207.43	7.418%	$222.8172	$222.82	$222.80	$222.80
Purchase #3	$156.25	7.129%	$167.3891	$167.39	$167.40	$167.40
Purchase #4	$96.28	4.817%	$100.9178	$100.92	$100.90	$100.90
Purchase #5	$102.50	11.452%	$114.2383	$114.24	$114.25	$114.20
Purchase #6	$8.83	10.329%	$9.7421	$9.74	$9.75	$9.70
Purchase #7	$247.37	10.873%	$274.2665	$274.27	$274.25	$274.30
7 purchase totals =	$1,014.54		$1,098.6845	$1,098.69	$1,098.65	$1,098.60