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	$139.83	7.271%	$149.997	$150.00	$150.00	$150.00
Purchase #2	$192.69	11.726%	$215.2848	$215.28	$215.30	$215.30
Purchase #3	$164.51	10.103%	$181.1304	$181.13	$181.15	$181.10
Purchase #4	$68.34	7.567%	$73.5113	$73.51	$73.50	$73.50
Purchase #5	$61.35	12.664%	$69.1194	$69.12	$69.10	$69.10
Purchase #6	$112.87	9.215%	$123.271	$123.27	$123.25	$123.30
Purchase #7	$233.81	12.697%	$263.4969	$263.50	$263.50	$263.50
7 purchase totals =	$973.40		$1,075.8108	$1,075.81	$1,075.80	$1,075.80