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	$52.56	3.712%	$54.511	$54.51	$54.50	$54.50
Purchase #2	$156.97	6.778%	$167.6094	$167.61	$167.60	$167.60
Purchase #3	$99.57	3.174%	$102.7304	$102.73	$102.75	$102.70
Purchase #4	$194.92	3.109%	$200.9801	$200.98	$201.00	$201.00
Purchase #5	$196.56	7.283%	$210.8755	$210.88	$210.90	$210.90
Purchase #6	$106.31	4.753%	$111.3629	$111.36	$111.35	$111.40
Purchase #7	$176.46	6.797%	$188.454	$188.45	$188.45	$188.50
7 purchase totals =	$983.35		$1,036.5233	$1,036.52	$1,036.55	$1,036.60