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	$212.67	10.144%	$234.2432	$234.24	$234.25	$234.20
Purchase #2	$173.66	12.458%	$195.2946	$195.29	$195.30	$195.30
Purchase #3	$168.73	13.345%	$191.247	$191.25	$191.25	$191.20
Purchase #4	$233.37	11.435%	$260.0559	$260.06	$260.05	$260.10
Purchase #5	$29.91	10.365%	$33.0102	$33.01	$33.00	$33.00
Purchase #6	$81.44	10.213%	$89.7575	$89.76	$89.75	$89.80
Purchase #7	$67.50	5.585%	$71.2699	$71.27	$71.25	$71.30
7 purchase totals =	$967.28		$1,074.8783	$1,074.88	$1,074.85	$1,074.90