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	$94.98	5.128%	$99.8506	$99.85	$99.85	$99.90
Purchase #2	$99.75	9.391%	$109.1175	$109.12	$109.10	$109.10
Purchase #3	$124.68	7.407%	$133.915	$133.92	$133.90	$133.90
Purchase #4	$112.25	13.489%	$127.3914	$127.39	$127.40	$127.40
Purchase #5	$210.64	6.320%	$223.9524	$223.95	$223.95	$224.00
Purchase #6	$148.90	11.696%	$166.3153	$166.32	$166.30	$166.30
Purchase #7	$204.73	13.410%	$232.1843	$232.18	$232.20	$232.20
7 purchase totals =	$995.93		$1,092.7265	$1,092.73	$1,092.70	$1,092.80