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	$243.67	10.366%	$268.9288	$268.93	$268.95	$268.90
Purchase #2	$198.57	3.822%	$206.1593	$206.16	$206.15	$206.20
Purchase #3	$53.46	10.449%	$59.046	$59.05	$59.05	$59.00
Purchase #4	$185.57	10.144%	$204.3942	$204.39	$204.40	$204.40
Purchase #5	$93.55	10.591%	$103.4579	$103.46	$103.45	$103.50
Purchase #6	$81.39	10.342%	$89.8074	$89.81	$89.80	$89.80
Purchase #7	$71.71	10.775%	$79.4368	$79.44	$79.45	$79.40
7 purchase totals =	$927.92		$1,011.2304	$1,011.24	$1,011.25	$1,011.20