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	$90.35	6.424%	$96.1541	$96.15	$96.15	$96.20
Purchase #2	$209.54	3.333%	$216.524	$216.52	$216.50	$216.50
Purchase #3	$242.53	10.596%	$268.2285	$268.23	$268.25	$268.20
Purchase #4	$142.35	8.512%	$154.4668	$154.47	$154.45	$154.50
Purchase #5	$232.44	9.862%	$255.3632	$255.36	$255.35	$255.40
Purchase #6	$184.77	6.840%	$197.4083	$197.41	$197.40	$197.40
Purchase #7	$136.91	5.848%	$144.9165	$144.92	$144.90	$144.90
7 purchase totals =	$1,238.89		$1,333.0614	$1,333.06	$1,333.00	$1,333.10