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	$199.87	7.852%	$215.5638	$215.56	$215.55	$215.60
Purchase #2	$16.90	3.781%	$17.539	$17.54	$17.55	$17.50
Purchase #3	$213.86	6.640%	$228.0603	$228.06	$228.05	$228.10
Purchase #4	$17.92	3.103%	$18.4761	$18.48	$18.50	$18.50
Purchase #5	$179.41	9.268%	$196.0377	$196.04	$196.05	$196.00
Purchase #6	$219.93	8.163%	$237.8829	$237.88	$237.90	$237.90
Purchase #7	$79.46	11.263%	$88.4096	$88.41	$88.40	$88.40
7 purchase totals =	$927.35		$1,001.9694	$1,001.97	$1,002.00	$1,002.00