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	$167.48	4.404%	$174.8558	$174.86	$174.85	$174.90
Purchase #2	$34.59	11.874%	$38.6972	$38.70	$38.70	$38.70
Purchase #3	$232.31	7.605%	$249.9772	$249.98	$250.00	$250.00
Purchase #4	$93.30	11.632%	$104.1527	$104.15	$104.15	$104.20
Purchase #5	$165.36	9.154%	$180.4971	$180.50	$180.50	$180.50
Purchase #6	$219.35	6.601%	$233.8293	$233.83	$233.85	$233.80
Purchase #7	$116.56	12.212%	$130.7943	$130.79	$130.80	$130.80
7 purchase totals =	$1,028.95		$1,112.8036	$1,112.81	$1,112.85	$1,112.90