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	$152.70	8.327%	$165.4153	$165.42	$165.40	$165.40
Purchase #2	$161.33	4.353%	$168.3527	$168.35	$168.35	$168.40
Purchase #3	$127.98	4.346%	$133.542	$133.54	$133.55	$133.50
Purchase #4	$250.79	7.866%	$270.5171	$270.52	$270.50	$270.50
Purchase #5	$249.67	9.714%	$273.9229	$273.92	$273.90	$273.90
Purchase #6	$32.85	9.784%	$36.064	$36.06	$36.05	$36.10
Purchase #7	$114.47	7.661%	$123.2395	$123.24	$123.25	$123.20
7 purchase totals =	$1,089.79		$1,171.0535	$1,171.05	$1,171.00	$1,171.00