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	$131.43	7.836%	$141.7289	$141.73	$141.75	$141.70
Purchase #2	$202.83	7.705%	$218.4581	$218.46	$218.45	$218.50
Purchase #3	$154.38	9.290%	$168.7219	$168.72	$168.70	$168.70
Purchase #4	$172.41	6.450%	$183.5304	$183.53	$183.55	$183.50
Purchase #5	$112.82	12.818%	$127.2813	$127.28	$127.30	$127.30
Purchase #6	$207.45	5.872%	$219.6315	$219.63	$219.65	$219.60
Purchase #7	$133.92	9.331%	$146.4161	$146.42	$146.40	$146.40
7 purchase totals =	$1,115.24		$1,205.7682	$1,205.77	$1,205.80	$1,205.70