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	$184.27	6.480%	$196.2107	$196.21	$196.20	$196.20
Purchase #2	$130.76	10.805%	$144.8886	$144.89	$144.90	$144.90
Purchase #3	$145.33	4.443%	$151.787	$151.79	$151.80	$151.80
Purchase #4	$43.68	4.826%	$45.788	$45.79	$45.80	$45.80
Purchase #5	$120.99	12.691%	$136.3448	$136.34	$136.35	$136.30
Purchase #6	$151.47	13.397%	$171.7624	$171.76	$171.75	$171.80
Purchase #7	$167.96	9.535%	$183.975	$183.98	$184.00	$184.00
7 purchase totals =	$944.46		$1,030.7565	$1,030.76	$1,030.80	$1,030.80