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	$242.65	4.628%	$253.8798	$253.88	$253.90	$253.90
Purchase #2	$156.83	7.274%	$168.2378	$168.24	$168.25	$168.20
Purchase #3	$103.98	13.307%	$117.8166	$117.82	$117.80	$117.80
Purchase #4	$240.91	11.350%	$268.2533	$268.25	$268.25	$268.30
Purchase #5	$109.40	4.558%	$114.3865	$114.39	$114.40	$114.40
Purchase #6	$61.63	8.196%	$66.6812	$66.68	$66.70	$66.70
Purchase #7	$59.39	9.206%	$64.8574	$64.86	$64.85	$64.90
7 purchase totals =	$974.79		$1,054.1126	$1,054.12	$1,054.15	$1,054.20