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	$229.33	6.163%	$243.4636	$243.46	$243.45	$243.50
Purchase #2	$159.31	13.543%	$180.8854	$180.89	$180.90	$180.90
Purchase #3	$14.94	6.369%	$15.8915	$15.89	$15.90	$15.90
Purchase #4	$248.84	7.566%	$267.6672	$267.67	$267.65	$267.70
Purchase #5	$183.48	4.170%	$191.1311	$191.13	$191.15	$191.10
Purchase #6	$63.66	5.351%	$67.0664	$67.07	$67.05	$67.10
Purchase #7	$79.58	7.471%	$85.5254	$85.53	$85.55	$85.50
7 purchase totals =	$979.14		$1,051.6306	$1,051.64	$1,051.65	$1,051.70