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	$133.88	6.107%	$142.0561	$142.06	$142.05	$142.10
Purchase #2	$130.66	6.685%	$139.3946	$139.39	$139.40	$139.40
Purchase #3	$7.52	8.510%	$8.16	$8.16	$8.15	$8.20
Purchase #4	$220.79	5.614%	$233.1852	$233.19	$233.20	$233.20
Purchase #5	$196.66	7.831%	$212.0604	$212.06	$212.05	$212.10
Purchase #6	$137.57	11.444%	$153.3135	$153.31	$153.30	$153.30
Purchase #7	$121.62	8.349%	$131.7741	$131.77	$131.75	$131.80
7 purchase totals =	$948.70		$1,019.9439	$1,019.94	$1,019.90	$1,020.10