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	$247.57	6.780%	$264.3552	$264.36	$264.35	$264.40
Purchase #2	$202.33	6.176%	$214.8259	$214.83	$214.85	$214.80
Purchase #3	$53.46	5.745%	$56.5313	$56.53	$56.55	$56.50
Purchase #4	$162.47	3.140%	$167.5716	$167.57	$167.55	$167.60
Purchase #5	$167.66	11.780%	$187.4103	$187.41	$187.40	$187.40
Purchase #6	$123.45	3.565%	$127.851	$127.85	$127.85	$127.90
Purchase #7	$64.65	12.567%	$72.7746	$72.77	$72.75	$72.80
7 purchase totals =	$1,021.59		$1,091.3199	$1,091.32	$1,091.30	$1,091.40