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	$204.37	5.414%	$215.4346	$215.43	$215.45	$215.40
Purchase #2	$185.81	3.141%	$191.6463	$191.65	$191.65	$191.60
Purchase #3	$92.77	3.809%	$96.3036	$96.30	$96.30	$96.30
Purchase #4	$245.66	8.465%	$266.4551	$266.46	$266.45	$266.50
Purchase #5	$7.99	4.272%	$8.3313	$8.33	$8.35	$8.30
Purchase #6	$36.93	9.565%	$40.4624	$40.46	$40.45	$40.50
Purchase #7	$176.48	11.328%	$196.4717	$196.47	$196.45	$196.50
7 purchase totals =	$950.01		$1,015.1050	$1,015.10	$1,015.10	$1,015.10