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	$210.49	5.683%	$222.4521	$222.45	$222.45	$222.50
Purchase #2	$16.87	8.282%	$18.2672	$18.27	$18.25	$18.30
Purchase #3	$119.86	13.850%	$136.4606	$136.46	$136.45	$136.50
Purchase #4	$35.36	6.124%	$37.5254	$37.53	$37.55	$37.50
Purchase #5	$218.69	4.727%	$229.0275	$229.03	$229.05	$229.00
Purchase #6	$204.33	12.153%	$229.1622	$229.16	$229.15	$229.20
Purchase #7	$187.73	6.289%	$199.5363	$199.54	$199.55	$199.50
7 purchase totals =	$993.33		$1,072.4313	$1,072.44	$1,072.45	$1,072.50