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	$103.70	7.481%	$111.4578	$111.46	$111.45	$111.50
Purchase #2	$27.53	13.501%	$31.2468	$31.25	$31.25	$31.20
Purchase #3	$207.84	3.798%	$215.7338	$215.73	$215.75	$215.70
Purchase #4	$168.44	12.487%	$189.4731	$189.47	$189.45	$189.50
Purchase #5	$144.30	4.117%	$150.2408	$150.24	$150.25	$150.20
Purchase #6	$143.71	5.708%	$151.913	$151.91	$151.90	$151.90
Purchase #7	$217.74	5.459%	$229.6264	$229.63	$229.65	$229.60
7 purchase totals =	$1,013.26		$1,079.6917	$1,079.69	$1,079.70	$1,079.60